1. The polyurethane hot melt adhesive is characterized by comprising the following preparation raw materials:

polyester polyol, wherein the average molar mass of the polyester polyol is not more than 6000 g/mol;

the thermoplastic polyester has the average molar mass of 2000-6000 g/mol;

the acrylate copolymer has the average molar mass of 30000-60000 g/mol;

polymeric diisocyanate, the average molar mass of the polymeric diisocyanate is more than or equal to 1000 g/mol.

2. The polyurethane hot melt adhesive according to claim 1, wherein the polyurethane hot melt adhesive is prepared from the following raw materials in parts by weight:

10-30 parts of polyester polyol;

10-30 parts of thermoplastic polyester;

5-15 parts of an acrylate copolymer;

40-60 parts of polymeric diisocyanate.

3. The polyurethane hot melt adhesive of claim 1, wherein the polyurethane hot melt adhesive is prepared from the following raw materials: chain extenders and catalysts; preferably, the chain extender comprises a compound shown in the following structural formula;

wherein, R, R₁And R₂Is any organic group or H;

further preferably, the catalyst comprises a tertiary amine catalyst.

4. The polyurethane hot melt adhesive according to any one of claims 1 to 3, wherein the polyester polyol is at least one of polyester diol and polyester triol.

5. The polyurethane hot melt adhesive according to any one of claims 1 to 3, wherein the thermoplastic polyester is prepared from polyester diol and monoisocyanate.

6. The polyurethane hot melt adhesive according to any one of claims 1 to 3, wherein the acrylate copolymer has a Tg < 45 ℃ < 110 ℃.

7. The polyurethane hot melt adhesive according to any one of claims 1 to 3, wherein the polymeric diisocyanate is prepared from polymeric diols and diisocyanates.

8. The polyurethane hot melt adhesive according to any one of claims 1 to 3, wherein the viscosity of the polyurethane hot melt adhesive at 90 ℃ to 110 ℃ is 4000 mPa-s to 20000 mPa-s.

9. The preparation method of the polyurethane hot melt adhesive as claimed in any one of claims 1 to 8, characterized by comprising the following steps:

s1, putting the polyester polyol, the thermoplastic polyester and the acrylate copolymer into a reaction kettle, and heating and dehydrating;

s2, maintaining the reaction temperature of the step S1, adding the polymeric diisocyanate, and reacting under a protective gas;

and S3, sequentially adding the chain extender and the catalyst into the system obtained in the step S2, and continuously reacting under a protective gas to obtain the polyurethane hot melt adhesive.

10. The use of the polyurethane hot melt adhesive as claimed in any one of claims 1 to 8 for bonding temperature-sensitive materials.

Background

The hot melt adhesive is a plastic adhesive, and is applied to a plurality of fields due to the advantages of rapid bonding, wide bonding range, repeated heating, repeated bonding, stable performance, low cost and the like. Hot melt adhesives currently on the market mainly comprise both reactive types (polyurethane, polyolefin and silicone) and non-reactive types (thermoplastic).

The initial adhesion of the hot melt adhesive is improved, and the hot melt adhesive is a hotspot of research in the technical field of hot melt adhesives. Among them, the most common method is to use a host resin (including reactive type and non-reactive type) having a molecular weight of several tens of thousands, hundreds of thousands or even hundreds of thousands, and the high molecular weight of the host resin causes high viscosity, and therefore, a common hot melt adhesive has a melt viscosity of several tens of thousands to several hundreds of thousands mPa · s even at a high sizing temperature, which causes inconvenience in sizing (high initial viscosity). Furthermore, the high sizing temperature brings about higher energy consumption on the one hand; on the other hand, when the gluing temperature is high, after cooling, large thermal stress is generated inside the hot melt adhesive and between the hot melt adhesive and the base material (the part to be bonded), so that the bonding firmness is reduced; most importantly, at high sizing temperatures, the active ingredients of reactive hot melt adhesives undergo a variety of side reactions, which in turn lead to failure of the hot melt adhesives.

Reducing the viscosity of the hot melt adhesive is also a research hotspot in the technical field of the hot melt adhesive. In order to reduce the viscosity, the following methods are commonly adopted in the industry; one is the addition of a plasticizer; the other is to use a low molecular weight tackifying resin (host resin) to reduce the viscosity; however, the two methods reduce the viscosity and directly reduce the initial adhesion. For reactive hot melt adhesives, the viscosity can be reduced by adding excessive isocyanate monomers in the industry, but the hot melt adhesives obtained by the method are easy to generate gases (isocyanate or decomposition products thereof) which pollute the air and influence the health of construction personnel in the using process; some of the commercial products reduce the viscosity by adding chain extenders to the raw materials, but this method reduces the initial viscosity as well as the viscosity.

In conclusion, the existing hot melt adhesive is difficult to realize high initial adhesion, low viscosity, excellent viscosity stability and environmental protection performance of the hot melt adhesive at the same time.

Disclosure of Invention

The present invention is directed to solving at least one of the problems of the prior art described above. Therefore, the polyurethane hot melt adhesive provided by the invention has the advantages that due to the matching of the raw materials, the obtained polyurethane hot melt adhesive has higher initial adhesion, lower viscosity and excellent viscosity stability, and simultaneously, the environmental friendliness in the use process is ensured.

The invention also provides a preparation method of the polyurethane hot melt adhesive.

The invention also provides application of the polyurethane hot melt adhesive in bonding temperature sensitive materials.

According to one aspect of the invention, the invention provides a polyurethane hot melt adhesive, which is prepared from the following raw materials:

polyester polyol, wherein the average molar mass of the polyester polyol is not more than 6000 g/mol;

the thermoplastic polyester has the average molar mass of 2000-6000 g/mol;

the acrylate copolymer has the average molar mass of 30000-60000 g/mol;

polymeric diisocyanate, the average molar mass of the polymeric diisocyanate is more than or equal to 1000 g/mol.

According to a preferred embodiment of the present invention, at least the following advantages are provided:

(1) the polyester polyol has reactivity (is an active raw material), and can further form a macromolecular main chain, so that the cohesive strength of the polyurethane hot melt adhesive obtained by the invention is increased; under the condition that other conditions are unchanged, the higher the average molar mass of the polyester polyol is, the higher the molecular weight of the main chain of the obtained polyurethane hot melt adhesive is, and further the initial adhesion and the viscosity are simultaneously improved;

the thermoplastic polyester has no reactivity and mainly has the function of adjusting the viscosity of the system; the average molar mass is high, the viscosity is high, and the effect of reducing the viscosity cannot be achieved; the average molar mass is low, so that the effect of increasing the initial adhesion and the cohesive strength of the system cannot be achieved; the average molar mass of the thermoplastic polyurethane commonly used in the field is generally more than or equal to 50000g/mol, and the thermoplastic polyurethane has no function of reducing the viscosity; the thermoplastic polyester adopted by the invention has smaller average molar mass, and can reduce the viscosity of the system to a certain degree;

the average molar mass of the acrylate copolymer adopted by the invention is closely related to the performance of the obtained polyurethane hot melt adhesive, the viscosity of the polyurethane hot melt adhesive is relatively increased when the average molar mass is too high, and the initial adhesion of the system is reduced when the average molar mass is too low;

at present, the diisocyanate with small molecules (non-polymeric, molar mass less than or equal to 500g/mol) is usually applied to the polyurethane hot melt adhesive, and the non-polymeric small molecules cannot be completely reacted in the preparation process, so that the residual diisocyanate can volatilize to generate gas in the application process, thereby causing the problems of environmental protection and occupational safety. Specifically, the method comprises the following steps:

in the preparation of the polyurethane hot melt adhesive, diisocyanate and polyol are subjected to prepolymerization reaction, a prepolymer A (n is more than or equal to 2) formed by n diisocyanate molecules and n-1 diol molecules is easily generated in the process, namely the consumption of the diisocyanate is less than that of the diol, so that a certain amount of unreacted diisocyanate monomer is remained; for example, in the synthesis of prepolymer a, when 10% (diisocyanate to the mass fraction of prepolymer a) of diphenylmethane diisocyanate (MDI) is added in a molar ratio NCO: OH of 2:1, about 2% of monomeric MDI is found in prepolymer a (product system); the monomers are easy to volatilize into the air in the sizing process (the volatilization degree is 150 ℃, and the vapor pressure of pure MDI is 0.8mBar), thereby causing occupational safety problems;

similar conclusions were also obtained by the Schulz-Flory statistical method: in the reaction of a diisocyanate having substantially the same reactivity with a hydroxyl compound, the residual monomeric diisocyanate content in the reaction product depends on the molar ratio of NCO: OH in the reactants, and when NCO: OH is 2:1, about 25% of the diisocyanate in the reactants remains in the form of monomer in prepolymer a (the amount of MDI added in the initial state is 10 wt%, so that 25% of the monomer remains, meaning that the mass of the residual monomer is 2.5% of the mass fraction of the product system); that is, the theoretical value and the calculated value differ by only 0.5%;

the polymeric diisocyanate provided by the invention has a prepolymerization reaction, is used as a raw material of a polyurethane hot melt adhesive, has an average molar mass of more than or equal to 1000g/mol, and can ensure that the polymeric diisocyanate has high activity and no volatility; meanwhile, compared with micromolecular diisocyanate (no polymerization reaction occurs), the activity of the prepolymer is reduced to a certain extent, but polymers are not easy to generate in the prepolymerization process of the prepolymer and polyester polyol (trimer is generated in the ideal situation of the invention), so that the molecular weight distribution of prepolymer B formed by the obtained polymeric diisocyanate and the polyester polyol is narrowed, free polymeric diisocyanate is reduced, side reactions are reduced in the continuous heating process, and the viscosity stability is improved; under the normal condition, the unused hot melt adhesive is repeatedly and continuously heated, so that the viscosity stability is improved, and the use of the obtained polyurethane hot melt adhesive is facilitated;

in conclusion, the polyurethane hot melt adhesive obtained by the invention through the collocation of the raw material components and the selection of the average molar mass of each component can simultaneously obtain higher initial adhesion, lower viscosity, excellent viscosity stability and environmental protection performance.

In some embodiments of the invention, the polyurethane hot melt adhesive is prepared from the following raw materials in parts by weight:

10-30 parts of polyester polyol;

10-30 parts of thermoplastic polyester;

5-15 parts of an acrylate copolymer;

40-60 parts of polymeric diisocyanate.

In some preferred embodiments of the present invention, the polyester polyol is added in an amount of 15 to 30 parts by weight.

In some preferred embodiments of the present invention, the polyester diol used as the polyester polyol has a Tm (melting temperature) >30 ℃.

The reason for limiting Tm is to ensure the initial adhesion of the polyurethane hot melt adhesive.

Because polyester polyol has reactivity and can generate macromolecules, the cohesive strength of the polyurethane hot melt adhesive is further increased, the adhesive force of the polyurethane hot melt adhesive is increased, the higher the addition amount of the polyester polyol is, the initial adhesive force of the obtained hot melt adhesive is improved, but the cooling speed of the adhesive is too high, so that the operable time is too short to form effective adhesion during application; if the addition amount is too small, the initial adhesion cannot be improved; therefore, the amount of 10 to 30 parts by weight is selected.

In some preferred embodiments of the present invention, the polyester polyol has an average molar mass of 2000 to 5000 g/mol.

In some embodiments of the present invention, the polyester polyol is at least one of a polyester diol and a polyester triol.

In some embodiments of the invention, the polyester polyol is a polyester diol.

The polyester triol contains 3 hydroxyl groups, so that if the polyester polyol is polyester triol, normal use can be ensured, but a certain degree of branched crosslinking may occur, and the viscosity is increased to a certain degree, so that the polyester polyol particularly preferred in the present invention is polyester diol.

In some embodiments of the present invention, the polyester diol used as the polyester polyol is poly (ethylene adipate) diol, poly (1, 4-butylene adipate) diol, poly (1, 6-hexanediol decaadipate) diol, poly (1, 6-hexanediol dodecanedioate) diol, poly (1, 6-hexanediol adipate) -ethylene glycol diol, poly (ethylene adipate) -1, 4-butylene glycol diol, poly (neopentyl adipate) diol, poly (diethylene adipate) -ethylene glycol diol, poly (diethylene glycol adipate) -ethylene glycol diol, poly (ethylene adipate) -1, 2-propylene glycol diol, poly (adipic acid-maleic anhydride-1, at least one of 4-butanediol diol, polyphthalate-diethylene glycol diol, polyhexamethylene isophthalate-butanediol diol, and polycaprolactone diol.

In some preferred embodiments of the present invention, the polyester diol used as the polyester polyol is at least one of poly-1, 4-butanediol adipate diol, poly-1, 6-hexanediol decamethylene adipate diol, poly-1, 6-hexanediol dodecanedioate, poly-1, 6-hexanediol adipate diol, and polycaprolactone diol.

In some embodiments of the invention, the thermoplastic polyester has an average molar mass of between 2000 and 5000 g/mol.

In some embodiments of the present invention, the thermoplastic polyester is added in an amount of 10 to 20 parts by weight.

The thermoplastic polyester has no reactivity, has the effect of adjusting the viscosity of the polyurethane hot melt adhesive, is small in average molar mass, namely the viscosity of the thermoplastic polyester is low, so that the more the amount of the thermoplastic polyester is, the lower the viscosity of the polyurethane hot melt adhesive is, but the cohesive strength of the obtained polyurethane hot melt adhesive is reduced to a certain extent, so that the bonding force is reduced, and therefore, the adding amount of 10-30 parts by weight is selected.

In some embodiments of the invention, the thermoplastic polyester, starting materials for the preparation comprise a polyester diol and a monoisocyanate.

When the thermoplastic polyester is prepared, isocyanate in the monoisocyanate and hydroxyl in the polyester diol react at a nearly equimolar ratio, and the content of residual hydroxyl in the obtained thermoplastic polyester is further reduced; hydroxyl groups are reactive groups, thus further reducing the reactivity of the resulting thermoplastic polyester.

In some embodiments of the present invention, the ratio of the molar amount of isocyanate groups in the monoisocyanate to the molar amount of hydroxyl groups in the polyesterdiol in the preparation of the thermoplastic polyester is (0.52-1.02): 1.

In some preferred embodiments of the present invention, the ratio of the molar amount of isocyanate groups in the monoisocyanate to the molar amount of hydroxyl groups in the polyesterdiol is about 0.98:1 when preparing the thermoplastic polyester.

In some embodiments of the invention, the polyester diol from which the thermoplastic polyester is made is poly (ethylene adipate) diol, poly (1, 4-butylene adipate) diol, poly (1, 6-hexanediol decaadipate) diol, poly (1, 6-hexanediol dodecanedioate) diol, poly (1, 6-hexanediol adipate) diol, poly (ethylene adipate) diol-1, 4-butylene diol, poly (neopentyl adipate) diol, poly (diethylene glycol adipate) diol, poly (ethylene adipate) diol-1, 2 propylene glycol diol, poly (adipic acid-maleic anhydride-1, at least one of 4-butanediol diol, polyphthalate-diethylene glycol diol, polyhexamethylene isophthalate-butanediol diol, and polycaprolactone diol.

In some preferred embodiments of the present invention, the polyester diol from which the thermoplastic polyester is made is at least one of poly-1, 4-butanediol adipate diol, poly-1, 6-hexanediol decamethylene adipate diol, poly-1, 6-hexanediol dodecanedioate, poly-1, 6-hexanediol adipate diol, and polycaprolactone diol.

If the polyester diols from which the thermoplastic polyesters are prepared are solid at room temperature (about 25 ℃), it is more advantageous for the initial adhesion of the resulting polyurethane hotmelt after cooling to be increased, and therefore for better achievement of high initial adhesion, the polyester diols preferably have a Tm of >30 ℃.

In some embodiments of the present invention, only monoisocyanates can be used and not polyisocyanates, for the preparation of the thermoplastic polyesters, since the polyester polyols obtained from the reaction of polyisocyanates having a number of functional groups > 1 still have reactive isocyanate residues, i.e.the resulting polyester polyols are still reactive; in the invention, in order to better adjust the viscosity of the polyurethane hot melt adhesive, the thermoplastic polyester is required to be inert to reaction.

In some embodiments of the present invention, the monoisocyanate from which the thermoplastic polyester is prepared comprises at least one of phenyl isocyanate, p-toluenesulfonyl isocyanate (CAS number: 4083-64-1), dodecyl isocyanate, and octadecyl isocyanate.

In some embodiments of the invention, the monoisocyanate from which the thermoplastic polyester is prepared comprises the tosyl isocyanate.

When the molar ratio of the isocyanic acid group in the tosyl isocyanate to the hydroxyl group in the polyester diol is slightly larger than 1:1, the hydroxyl group in the polyester diol can be ensured to be completely reacted, meanwhile, the tosyl amide produced by the reaction of the tosyl isocyanate and the water has no reactivity, the viscosity of a system is not increased, the influence of the isocyanic acid group on the activity of the thermoplastic polyester is not needed to be further considered, and the influence of trace water in the system on the viscosity of the system can be reduced.

In some embodiments of the present invention, when the monoisocyanate from which the thermoplastic polyester is made comprises the tosyl isocyanate, the preferred molar ratio of isocyanate groups in the monoisocyanate to hydroxyl groups in the polyesterdiol is about 1.02: 1.

When the monoisocyanate includes at least one of phenyl isocyanate, dodecyl isocyanate and octadecyl isocyanate in preparing the thermoplastic polyester, the addition of an excessive amount of the monoisocyanate is avoided; the reason for this is that some of the isocyanates mentioned above react with water to form primary amino groups containing two active hydrogens, which further cross-react with the polymeric diisocyanate, resulting in an unpredictable increase in viscosity.

In some embodiments of the present invention, when preparing the thermoplastic polyester, the preparation method comprises the steps of:

A1. melting the polyester diol and performing dehydration treatment;

A2. and D, adding the monoisocyanate into the system obtained in the step A1, and reacting to obtain the thermoplastic polyester.

In some embodiments of the present invention, the melting in step A1 is performed at a temperature of about 110-130 ℃.

In some preferred embodiments of the present invention, in step A1, the melting temperature is about 120 ℃.

In some embodiments of the present invention, in step A1, the polyester diol has a water content of 200ppm or less after the dehydration treatment.

In some embodiments of the present invention, in the step A2, the reaction time is about 1 to 1.5 hours.

In some preferred embodiments of the present invention, in step a2, the reaction is carried out for about 1 hour.

In some embodiments of the present invention, the acrylate copolymer is added in an amount of 5 to 12 parts by weight.

The addition amount of the acrylate copolymer is closely related to the viscosity and initial adhesion of the obtained polyurethane hot melt adhesive, when the addition amount is too much (more than 15 parts by weight), the viscosity of the system is sharply increased and the compatibility with a matrix (an adhered part) is reduced, and when the addition amount is too little, the initial adhesion of the system cannot be effectively improved.

In some embodiments of the invention, the acrylate copolymer, 45 ℃ < Tg (glass transition temperature) < 110 ℃.

The higher the Tg value of the acrylate copolymer is, the higher the cooling speed of the polyurethane hot melt adhesive is in the using process, and the more effectively the initial adhesion of the polyurethane hot melt adhesive can be improved; however, if the Tg value of the acrylate copolymer is too high, the melting difficulty of the obtained polyurethane hot melt adhesive is increased, and the compatibility of the acrylate copolymer with other components of the system is reduced, so that the adhesive cannot be normally discharged, and therefore, the invention balances the performances in all aspects, and selects the range of the Tg value.

In some embodiments of the invention, the acrylate copolymer is derived from a linear or branched C of (meth) acrylic acid₁-C₁₈Alkyl ester, and at least one unsaturated compound containing double bond.

The double bond-containing unsaturated compound includes C of an olefinic acid (e.g., crotonic acid or maleic acid)₁-C₁₈Esters (linear or branched), (meth) acrylic acid with glycol ethers (e.g. methoxyethanol, ethoxyethanol, polyethylene glycol mono-or poly-ethylene glycol)Ethers), vinyl esters (e.g., vinyl acetate, vinyl propionate, vinyl esters of branched monocarboxylic acids), and vinyl aromatic hydrocarbons.

The acrylate copolymer is an inactive raw material, namely plays a role in adjusting viscosity and initial viscosity in the polyurethane hot melt adhesive.

In some embodiments of the present invention, the polymeric diisocyanate has an average molar mass of 1200 to 2000 g/mol.

In the preparation process of the polyurethane hot melt adhesive, the polymeric diisocyanate and the polyester polyol can be subjected to prepolymerization reaction to obtain prepolymer B.

The prepolymer A in the present invention refers to a polymerization product of diisocyanate (monomer) and polyol.

In the present invention, the prepolymer B refers to the polymerization product of the polymeric diisocyanate and the polyester polyol, wherein a part of the non-reactive thermoplastic polyester and the acrylate copolymer may be further included.

The polymeric diisocyanates used in the present invention can be prepared commercially or in the laboratory.

In some embodiments of the present invention, the polymeric diisocyanate, the starting materials for the preparation include polymeric diols and diisocyanates.

In some embodiments of the present invention, the molar ratio of isocyanate groups in the diisocyanate to hydroxyl groups in the polymeric diol is (1.8-2.2): 1 when the polymeric diisocyanate is prepared.

If the content of the isocyanic acid radical in the diisocyanate is too high, the viscosity of the obtained polyurethane hot melt adhesive is reduced, but a more serious bubble problem can be caused;

if the content of the isocyanate group in the diisocyanate is too low, the adhesive force of the obtained polyurethane hot melt adhesive is reduced.

In some embodiments of the present invention, the polymeric glycol has a molecular weight of 500g/mol or more.

In some embodiments of the invention, the polymeric glycol comprises at least one of poly (adipic acid-neopentyl glycol ester) glycol, poly (adipic acid-diethylene glycol ester) glycol, poly (phthalic anhydride-diethylene glycol ester) glycol, polyethylene glycol, polypropylene glycol, and polytetrahydrofuran glycol.

In some preferred embodiments of the present invention, the polymeric glycol comprises a poly phthalic anhydride-diethylene glycol ester diol.

The phthalic anhydride-diethylene glycol ester diol can effectively improve the adhesive force and cohesive strength of the polyurethane hot melt adhesive.

In some preferred embodiments of the present invention, the polymeric glycol comprises polypropylene glycol.

The polymeric diisocyanate prepared from the polypropylene glycol can effectively reduce the viscosity of the obtained polyurethane hot melt adhesive and simultaneously increase the compatibility of the acrylate copolymer with other preparation raw materials.

In some embodiments of the present invention, the diisocyanate is at least one of diphenylmethane diisocyanate (MDI), Hexamethylene Diisocyanate (HDI), Naphthalene Diisocyanate (NDI), p-phenylene diisocyanate (PPDI), isophorone diisocyanate (IPDI), Xylylene Diisocyanate (XDI), Toluene Diisocyanate (TDI), polymethylene polyphenyl diisocyanate (PAPI), methylcyclohexyl diisocyanate (HTDI), dicyclohexylmethane diisocyanate (HMDI), 1, 4-cyclohexane diisocyanate (CHDI), and 4,4 '-diphenylmethane diisocyanate (4, 4' -MDI).

In some preferred embodiments of the present invention, the diisocyanate is at least one of MDI, NDI, and 4, 4' -MDI.

In some further preferred embodiments of the present invention, the diisocyanate is 4, 4' -MDI.

In some embodiments of the invention, when the addition amount of the polymeric diisocyanate is 40-60 parts by weight, the mass percentage of NCO groups in the polyurethane hot melt adhesive is 1.5-3.0%.

The polyester diols used as the polyester polyol, the polyester diols used for the synthesis of the thermoplastic polyester, and the polymeric diols used for the synthesis of the polymeric diisocyanates may be identical, partially identical, or completely different.

In some embodiments of the present invention, the preparation raw materials of the polyurethane hot melt adhesive further include: chain extenders and catalysts.

In some embodiments of the present invention, the chain extender is added in an amount of 1 to 10 parts by weight.

In some embodiments of the present invention, the chain extender is added in an amount of 2 to 5 parts by weight.

And if too much chain extender is added, most of NCO groups in the prepolymer B participate in chain extension and crosslinking, the chemical reaction between the prepolymer B and an adhesive base material is reduced, and the adhesive force is reduced, and if too little chain extender is added, the chain extension and crosslinking effects cannot be achieved.

In some embodiments of the present invention, the chain extender comprises a compound represented by the following structural formula;

wherein, R, R₁And R₂Is any organic group or H.

In some embodiments of the invention, the chain extender comprises at least one of 3-ethyl-2-methyl-2 (3-methylbutyl) -1, 3-oxazolidine (CAS number: 143860-04-2), 3-butyl-2- (1-ethylpentyl) oxazolidine (CAS number: 165101-57-5), 2-isopropyl-3-oxazolidineethanol (CAS number: 219987-01-6), and 1, 6-hexanediylbis (bis {2- [2- (3-heptylalkyl) -1, 3-oxazolidin-3-yl ] ethyl } carbamate) (CAS number: 140921-24-0).

In some preferred embodiments of the invention, the chain extender comprises at least one of 3-ethyl-2-methyl-2 (3-methylbutyl) -1, 3-oxazolidine, 3-butyl-2- (1-ethylpentyl) oxazolidine, and 1, 6-hexanediylbis (bis {2- [2- (3-heptanyl) -1, 3-oxazolidin-3-yl ] ethyl } carbamate); the chain extender is an oxazolidine compound without hydroxyl groups before hydrolysis, so that the chain extender can better play a role in reducing viscosity.

In some preferred embodiments of the invention, the chain extender comprises 1, 6-hexanediylbis (bis {2- [2- (3-heptanyl) -1, 3-oxazolidin-3-yl ] ethyl } carbamate); the chain extender contains two oxazolidine groups, and four groups capable of reacting with NCO are generated after hydrolysis, so that the curing speed and the chain extension speed can be further accelerated, and the cohesive strength of the obtained polyurethane hot melt adhesive is improved.

In some preferred embodiments of the invention, the

Part of the action mechanism of the chain extender is shown as the following formula:

specifically, the action mechanism of the oxazolidine chain extender is as follows: after sizing, oxazolidine compounds in the polyurethane hot melt adhesive react with water in the air to generate secondary amino alcohol, and secondary amino groups and hydroxyl groups can react with NCO in the prepolymer B to play a role in chain extension;

in addition, the chain extender has a certain viscosity increasing effect, and the chain extender acts after the prepolymerization of the polymeric diisocyanate and the polyester polyol, namely the chain extender has no influence on the viscosity of the polyurethane hot melt adhesive, so that the viscosity of the polyurethane hot melt adhesive obtained by the invention is relatively low in use; but through moisture curing after gluing, the curing speed and the chain extension speed are both improved, which is beneficial to improving the cohesive strength of the polyurethane hot melt adhesive, namely, the adoption of oxazolidine chain extender can not influence the viscosity of the polyurethane hot melt adhesive, and can improve the adhesive force and the cohesive strength of the hot melt adhesive.

In some embodiments of the present invention, the catalyst is added in an amount of 0.01 to 0.1 parts by weight.

In some preferred embodiments of the present invention, the catalyst is added in an amount of 0.01 to 0.05 parts by weight.

In some embodiments of the invention, the catalyst comprises a tertiary amine catalyst.

In some embodiments of the invention, the catalyst comprises at least one of triethylenediamine, cyclohexylmethyl tertiary amine, pentamethyl dialkylene triamine, tetramethyl alkylene diamine, dimethyl ethanol amine, dimethylaminoethoxyethanol, trimethyl hydroxyethyl propylene diamine, trimethyl hydroxyethyl ethylene diamine, tetramethyl dipropylene triamine, 1, 4-dimethyl piperazine, N-methyl morpholine, N-ethyl morpholine, bis morpholinyl diethyl ether, N-methyl imidazole, and 1, 2-methyl imidazole.

In some preferred embodiments of the invention, the catalyst comprises at least one of N-methylmorpholine, N-ethylmorpholine, and dimorpholinodiethylether; the catalyst is selected, so that the reaction speed of gel, catalysis and water can be effectively balanced.

In the traditional polyurethane hot melt adhesive, metal catalysts such as organic tin and the like are usually adopted, the catalysts have low activity of catalyzing the reaction between isocyanate and water, and the activity of catalyzing isocyanate, carbamate and allophanate is high; therefore, the catalyst can not play an effective role in the wet curing engineering after the glue is applied to the hot melt adhesive, but the side reaction is easily promoted in the prepolymerization process, so that the phenomena of viscosity increase and even gel failure and the like are caused;

in comparison, the tertiary amine catalyst adopted by the invention has high activity for catalyzing the reaction between isocyanate and water, and low activity for catalyzing the reaction between isocyanate, carbamate and allophanate, so that the conditions of viscosity increase, even gelation and the like caused by side reaction in the prepolymerization process can be reduced to a certain extent; therefore, the adhesive force of the obtained polyurethane hot melt adhesive can be improved, and the viscosity of the polyurethane hot melt adhesive is reduced.

In some embodiments of the present invention, the polyurethane hot melt adhesive has a viscosity of 4000 to 20000 mPa-s at 90 to 110 ℃.

According to the polyurethane hot melt adhesive provided by the invention, in the process of naturally cooling the polyurethane hot melt adhesive after being heated and melted to become a solid, the adhesive force with a base material is rapidly improved, the next process can be rapidly carried out, and the polyurethane hot melt adhesive is further solidified through moisture in the subsequent process, so that the adhesive force is improved.

According to still another aspect of the present invention, a preparation method of the polyurethane hot melt adhesive is provided, which comprises the following steps:

s1, putting the polyester polyol, the thermoplastic polyester and the acrylate copolymer into a reaction kettle, and heating and dehydrating;

s2, maintaining the reaction temperature of the step S1, adding the polymeric diisocyanate, and reacting under a protective gas;

and S3, sequentially adding the chain extender and the catalyst into the system obtained in the step S2, and continuously reacting under a protective gas to obtain the polyurethane hot melt adhesive.

In some embodiments of the present invention, in step S1, the heating is performed at a temperature of 100-130 ℃.

In some embodiments of the invention, in step S1, the dehydration is performed by vacuum stirring.

And stirring in vacuum for 1-3 h, wherein the vacuum degree is-0.095-0.05 MPa.

In some embodiments of the present invention, in step S2, the reaction is performed for 1 to 3 hours under stirring conditions.

In some embodiments of the present invention, in step S3, the reaction is performed for 0.5 to 2 hours under stirring conditions.

In some embodiments of the invention, the reaction temperature of the preparation method of the polyurethane hot melt adhesive is 100-130 ℃.

In some embodiments of the present invention, the protective gas is at least one of nitrogen and an inert gas.

According to a further aspect of the present invention, the use of the polyurethane hot melt adhesive for bonding temperature sensitive materials is proposed.

In some embodiments of the invention, the temperature sensitive material comprises at least one of a film, a plastic, and paper.

Detailed Description

The concept and technical effects of the present invention will be clearly and completely described below in conjunction with the embodiments to fully understand the objects, features and effects of the present invention. It is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments, and those skilled in the art can obtain other embodiments without inventive effort based on the embodiments of the present invention, and all embodiments are within the protection scope of the present invention.

In the description of the present invention, reference to the description of the terms "one embodiment," "some embodiments," "an illustrative embodiment," "an example," "a specific example," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

Example 1

The embodiment provides a polyurethane hot melt adhesive, and the specific raw material composition is shown in table 1.

TABLE 1 raw material compositions of polyurethane hot melt adhesives obtained in examples 1 to 4 and comparative examples 1 to 4

Wherein unfilled cells indicate no additions.

Unless otherwise specified, the sources of the raw materials in table 1 are as follows:

polyester polyol 1 model Dynacoll 7360 (crystalline); polyester polyol 2 model number Dynacoll 7381 (crystalline); the type 3 of polyester polyol is Dynacoll 7250 (liquid), and the three polyester polyols are purchased from winning industrial group;

thermoplastic polyester 1 had a composition of a mixture of Dynacoll 7360 (average molar mass 3500g/mol) and SUPERSORB-TI, in which NCO: OH ═ 1.02:1 (molar ratio);

thermoplastic polyester 2 had a composition of Dynacoll7361 (average molar mass 8500g/mol) and SUPERSORB-TI, where NCO: OH ═ 1.02:1 (molar ratio);

wherein SUPERSORB-TI is p-toluenesulfonyl isocyanate purchased from the ocean of Yingzhou, Korea; dynacoll7361 (crystalline form) was purchased from winning industrial group;

the acrylate copolymer is a copolymer of methyl methacrylate and butyl acrylate which is purchased from the Luchoite International and has the model number of Elvcite 2013;

the polymeric diisocyanate 1 is a mixture of PDP-70 and Desmodur 44MC, NCO: OH is 2.1:1 (molar ratio);

the polymeric diisocyanate 2 is a mixture of PPG 1000 and Desmodur 44MC, NCO: OH 2.05:1 (molar ratio);

wherein PDP-70 is poly phthalic anhydride-diethylene glycol ester diol produced by Spirallon USA; PPG 1000 is 1000g/mol of polypropylene glycol produced by Jinling petroleum; desmodur 44MC is MDI produced by scientific Innovation in Germany;

the diisocyanate is Desmodur 44 MC;

the chain extender is produced by hederide, and the model ALT-402 is an oxazolidine compound (CAS number: 140921-24-0);

the catalyst is dimorpholinodiethylether available from Hensman, USA, and the model is Jeffcat DMDEE (CAS number: 6425-39-4);

the raw materials are all directly used without any pretreatment.

Examples 2 to 4 and comparative examples 1 to 4 respectively provide a polyurethane hot melt adhesive, and specifically, the polyurethane hot melt adhesive is different from example 1 in preparation raw materials, and the specific preparation raw materials are shown in table 1.

Test examples

The performance of the polyurethane hot melt adhesives obtained in the examples and comparative examples was tested in this test example. Wherein:

testing the initial adhesion of the obtained polyurethane hot melt adhesive according to the testing method given in GB/T7124-2008 (the PC/PC tensile shear strength of the sample is tested after the sample is cured for 15min under the condition of 25 ℃/50% RH, if the initial adhesion is specially stated, the initial adhesion refers to the concept in the invention), and the final adhesion (the PC/PC tensile shear strength of the sample is tested after the sample is cured for 7d under the condition of 25 ℃/50% RH, if the initial adhesion is not specially stated, the adhesion refers to the concept in the invention);

the melt viscosity of the obtained polyurethane hot melt adhesive and the melt viscosity after aging at 110 ℃ for 8h were tested according to the test method given in ASTM D3236-1988. The test results are shown in table 2.

Table 2 Performance results of the polyurethane hot melt adhesives obtained in examples 1 to 4 and comparative examples 1 to 4

The viscosity stability of the polyurethane hot melt adhesive obtained by the invention can be known by comparing the value of the aged viscosity at 110 ℃ with the value of the aged viscosity at 110 ℃.

As can be seen from Table 2, the polyurethane hot melt adhesives obtained in examples 1-4 have low residual isocyanate, high initial adhesion and final adhesion, low viscosity and excellent properties.

Compared with the comparative example 1, in the comparative example 1 (a formula of a relatively common reaction type polyurethane hot melt adhesive on the market), no thermoplastic polyester or chain extender is added, meanwhile, the polymeric diisocyanate is replaced by diisocyanate, the adopted polyester polyol also comprises liquid polyester polyol 3, the viscosity of the obtained polyurethane hot melt adhesive is increased, the viscosity stability is poor, and the sizing is not facilitated.

Examples in comparison with comparative example 2, comparative example 2 employs a thermoplastic polyester in which the average molar mass of the polymeric polyol is 8500g/mol (Dynacoll 7361), and thus the average molar mass of the resulting thermoplastic polyester is also greatly increased, and the viscosity of the resulting polyurethane hot melt adhesive is increased, which is detrimental to sizing.

Examples in comparison with comparative example 3, in comparative example 3, no polyester polyol was added, that is, no macromolecular main chain could be formed, and although the initial adhesion was substantially unchanged, the viscosity was reduced and the adhesion was greatly reduced.

In the examples, compared with comparative example 4, the content of the acrylate copolymer in comparative example 4 is beyond the range provided by the present invention, and the initial adhesion is improved but the viscosity is obviously increased without adding the thermoplastic polyester.

The embodiments of the present invention have been described in detail, but the present invention is not limited to the embodiments, and various changes can be made without departing from the gist of the present invention within the knowledge of those skilled in the art. Furthermore, the embodiments of the present invention and the features of the embodiments may be combined with each other without conflict.