1. A chlorination modification method of resin with high vinyl acetate content is characterized in that the chlorination modification method is a gas-solid phase chlorination modification method, and the vinyl acetate content in the resin is 30% -36%.

2. The method for modifying a resin with high vinyl acetate content according to claim 1, wherein the method comprises the following steps:

s1, adding an ethylene-vinyl acetate polymer, a vinyl acetate monomer, an initiator and a dispersing agent into a reaction kettle, and stirring and mixing uniformly;

s2, introducing chlorine into the reaction kettle in the step S1 for 10-15min, then heating the reaction kettle, continuing stirring, and stably introducing chlorine for reaction;

s3, stopping introducing chlorine after the reaction in the step S2 is finished, preserving heat for 1-2h, removing residual chlorine in the reaction kettle by using nitrogen, pumping out gas in the reaction kettle by using a vacuum pump, and reducing the temperature and pressure;

and S4, after the temperature and pressure reduction in the step S3 is finished, taking out the sample, and naturally cooling to obtain the resin with high vinyl acetate content.

3. The method of claim 2, wherein in step S1, the ethylene-vinyl acetate polymer is 100 parts, the vinyl acetate monomer is 5-12 parts, the initiator is 0.3-2 parts, and the dispersant is 1-3 parts.

4. The method of claim 2 or 3, wherein the ethylene-vinyl acetate polymer has a vinyl acetate content of 28%.

5. The method for modifying a resin having a high vinyl acetate content by chlorination as claimed in claim 2 or 3, wherein the initiator is one or both of benzoyl peroxide and cyclohexanone peroxide.

6. The method of claim 2 or 3, wherein the dispersant in step S1 is one or more selected from silicon dioxide, magnesium silicate, and calcium silicate.

7. The method of claim 2, wherein the amount of chlorine gas introduced in step S2 is 3-5 times the weight of the ethylene-vinyl acetate.

8. The method of claim 2, wherein the chlorination reaction conditions in step S2 are as follows: the reaction temperature is 100-140 ℃, the reaction pressure is 0.5-0.8MPa, and the reaction time is 3-6 h.

9. The method for modifying the chlorination of resin with high vinyl acetate content according to claim 2, wherein the temperature of the reaction kettle in the step S3 is reduced to 45-70 ℃, and the pressure is reduced to normal pressure.

10. Use of a chlorinated modified resin according to any one of claims 1 to 9 in a cable material.

Background

Vinyl Acetate (VA) is an important organic raw material, and is one of the most important 50 organic chemical raw materials in the world. In practical use, vinyl acetate can be polymerized by itself or with other monomers to form derivatives such as mainly polyvinyl acetate (PVA), polyvinyl alcohol (PVOH), vinyl acetate-ethylene copolymer Emulsion (EVA), vinyl acetate-vinyl chloride copolymer (EVC), polyethylene comonomer, and acetal resin. The derivatives have wide application in the aspects of coatings, sizing agents, adhesives, vinylon, films, leather processing, synthetic fibers, soil improvement and the like, for example, the polyvinyl alcohol is mainly used for producing vinylon, textile sizing agents, coatings, adhesives, paper reinforcing agents and coatings, industrial polymerization aids and the like; the vinyl acetate-ethylene copolymer resin and the vinyl acetate-vinyl chloride copolymer can be widely used in the production fields of foamed shoe materials, functional greenhouse films, packaging films, hot melt adhesives, wires and cables, toys and the like.

EVA has good impact resistance and stress cracking resistance, flexibility, high elasticity, tear resistance, puncture resistance, low density, good electrical property and chemical stability, and has good compatibility with filler and flame retardant. The vinyl acetate content of industrial products is 5% -95%, and the EVA is generally classified according to the content of the vinyl acetate, and can be divided into three types: the EVA resin with the VA content of 5-40 percent is mainly used for modifying polyethylene, manufacturing wire and cable materials, films and other molded products; the VA content of 40-70% is generally called as EVA elastic resin and is mainly used for rubber elastomers, PVC modifiers and the like; EVA with VA content of 70-95% is generally in emulsion state and is mainly used as adhesive base material, coating and paint. Generally, as the vinyl acetate content increases, the crystallinity hardness rigidity and heat distortion temperature gradually decrease, while the gloss, transparency, impact resistance, flexibility, stress crack resistance, solubility in solvents, heat shrinkage, heat weldability, and the like increase to various degrees. How to maintain good crystallinity and hardness and have high heat distortion temperature under the condition of higher vinyl acetate content needs to find a good modification method. At present, a plurality of modification methods are adopted by a solution chlorination method and a water phase chlorination method, but the solution method needs an organic solvent, and the chlorine content is not well controlled; although the aqueous phase method can not use organic solvent, the method belongs to heterogeneous reaction, has poor chlorination uniformity and is easy to corrode equipment.

Disclosure of Invention

The invention aims to provide a chlorination modification method of resin with high vinyl acetate content, which adopts a gas-solid phase chlorination modification method to uniformly distribute chlorine atoms in ethylene-vinyl acetate resin, improves the fluidity of the resin, grafts vinyl acetate into the ethylene-vinyl acetate resin in a chlorination manner, improves the vinyl acetate content, and simultaneously maintains the original performance, the vinyl acetate content of the chlorinated and modified EVA resin is between 30 and 36 percent, has good crystallinity, hardness and thermal deformation temperature, and simultaneously improves the mechanical properties such as tensile strength, flexibility and the like; the method has reliable process, simple operation and no pollution.

In order to achieve the purpose, the invention discloses a chlorination modification method of resin with high vinyl acetate content, which is a gas-solid phase chlorination modification method, wherein the vinyl acetate content in the resin is between 30 and 36 percent.

In the technical scheme, a sample of the gas-phase chlorination modification method is in a solid state, and better comprehensive performance can be obtained through the direct reaction of gas and solid; the whole process does not use organic solvent, can avoid the pollution of the organic solvent, can also avoid the corrosion of HCl, and almost does not have the discharge of three wastes. The content of vinyl acetate in the EVA resin is improved to 30-36%, so that the characteristics of the original resin are maintained, and the flow property and the mechanical property are improved.

Further, the chlorination modification method in the technical scheme comprises the following specific steps:

s1, adding an ethylene-vinyl acetate polymer, a vinyl acetate monomer, an initiator and a dispersing agent into a reaction kettle, and stirring and mixing uniformly;

s2, introducing chlorine into the reaction kettle in the step S1 for 10-15min, then heating the reaction kettle, continuing stirring, and stably introducing chlorine for reaction;

s3, stopping introducing chlorine after the reaction in the step S2 is finished, preserving heat for 1-2h, removing residual chlorine in the reaction kettle by using nitrogen, pumping out gas in the reaction kettle by using a vacuum pump, and reducing the temperature and pressure;

and S4, after the temperature and pressure reduction in the step S3 is finished, taking out the sample, and naturally cooling to obtain the resin with high vinyl acetate content.

The reaction mechanism in the technical scheme is as follows: uniformly mixing the components to obtain a certain wet solid mixture, then reacting the mixture with chlorine under the condition of heating and pressurizing, wherein one chlorine radical replaces a hydrogen atom on an ethylene-vinyl acetate polymer skeleton structure to form HCl gas, and the other chlorine radical is connected to the ethylene-vinyl acetate polymer structure; and when the vinyl acetate monomer exists in the system, the vinyl acetate monomer reacts with the polymer to form a branched chain of the polymer, and meanwhile, due to the heterogeneous system, the grafted ethylene-vinyl acetate polymer is continuously chlorinated when meeting chlorine free radicals. The invention modifies the ethylene-vinyl acetate polymer by chlorine gas, grafts the vinyl acetate monomer on the polymer, and continues chloridizes the grafted ethylene-vinyl acetate polymer resin, thereby not only increasing the content of vinyl acetate of the resin, but also uniformly distributing chlorine atoms in the resin, and improving the comprehensive performance of the resin. The HCl gas generated is discharged from the other end of the chlorine input end and is introduced into water to be absorbed by the water, and the HCl gas can be recycled without pollution.

Further, in the step S1 of the above technical scheme, 100 parts of ethylene-vinyl acetate polymer, 5-12 parts of vinyl acetate monomer, 0.3-2 parts of initiator and 1-3 parts of dispersant are used.

Further, in the above technical scheme, the content of vinyl acetate in the ethylene-vinyl acetate polymer is 28%. In the technical scheme, the EVA content is 28%, the EVA is generally used for preparing the wire cable material, the toughness and the impact resistance are good, but the crystallinity, the hardness and the heat distortion temperature are relatively poor.

Further, in the above technical scheme, the initiator is one or two of benzoyl peroxide and cyclohexanone peroxide.

In the technical scheme, the benzoyl peroxide is a strong oxidant and can be used as an initiator of synthetic resin; cyclohexanone peroxide is a white powder that can be used as a polymerization initiator for rubber and synthetic resins; the initiator is heated and decomposed into free radicals, and can be used for initiating free radical polymerization and copolymerization of alkene and diene monomers.

Further, in the above technical solution, in step S1, the dispersant is one or more of silicon dioxide, magnesium silicate, and calcium silicate. The dispersing agent in the technical scheme mainly has the effects of shortening the dispersing time of raw materials and simultaneously increasing the stability of a mixture.

Furthermore, the chlorine gas introduction amount in the step S2 of the technical scheme is 3-5 times of the weight part of the ethylene-vinyl acetate.

In the technical scheme, excessive chlorine is introduced, so that a large amount of C1-free radicals are continuously generated in the system, the activation and termination of chains are facilitated, and the product has a structure of multiple branch points and extremely short branch chains.

Further, the chlorination reaction conditions in step S2 of the above technical scheme are: the reaction temperature is 100-140 ℃, the reaction pressure is 0.5-0.8MPa, and the reaction time is 3-6 h.

According to the technical scheme, chlorine is decomposed into chlorine radicals under high temperature and high pressure, the reaction among the polymer, the chlorine radicals and the monomer is facilitated, and the chlorination modification is thorough.

Further, in the technical scheme, in the step S3, the temperature of the reaction kettle is reduced to 45-70 ℃, and the pressure is reduced to normal pressure.

The invention also provides an application of the chlorinated modified resin in cable materials.

The invention has the beneficial effects that:

1. according to the invention, the ethylene-vinyl acetate polymer is modified by chlorine gas, the vinyl acetate monomer is grafted to the polymer, and the grafted ethylene-vinyl acetate polymer resin is chlorinated continuously, so that the content of vinyl acetate in the resin is increased, chlorine atoms are uniformly distributed in the resin, and the comprehensive performance of the resin is improved;

2. the HCl gas generated in the chlorination modification method is discharged from the other end of the input chlorine gas and is introduced into water to be absorbed by water, so that the HCl gas can be recycled and is pollution-free;

3. the content of vinyl acetate in the chlorinated and modified EVA resin is 30-36%, the chlorinated and modified EVA resin has good crystallinity, hardness and thermal deformation temperature, and the mechanical properties such as tensile strength, flexibility and the like are improved, so that the chlorinated and modified EVA resin can be applied to cable materials;

3. the chlorination modification method has the advantages of reliable process, simple operation and no pollution.

Detailed Description

The experimental procedures in the following examples are conventional unless otherwise specified. The raw materials in the following examples are all commercially available products and are commercially available, unless otherwise specified.

The present invention is described in further detail below with reference to examples:

example 1

A chlorination modification method of resin with high vinyl acetate content specifically comprises the following specific steps:

s1, adding 100 parts of ethylene-vinyl acetate polymer, 8 parts of vinyl acetate monomer, 0.3 part of initiator and 3 parts of dispersant into a reaction kettle, and stirring and mixing uniformly;

s2, introducing chlorine into the reaction kettle in the step S1 for 10min, then heating the reaction kettle, continuing stirring, and stably introducing the chlorine for reaction, wherein the amount of the chlorine is 5 times of the weight of the ethylene-vinyl acetate, and the chlorination reaction conditions are as follows: the reaction temperature is 100 ℃, the reaction pressure is 0.5MPa, and the reaction time is 6 h;

s3, stopping introducing chlorine after the reaction in the step S2 is finished, preserving heat for 2 hours, then using nitrogen to drive off the residual chlorine in the reaction kettle, cooling to 50 ℃, and reducing the pressure to normal pressure;

and S4, after the temperature and pressure reduction in the step S3 is finished, taking out the sample, and naturally cooling to obtain the resin with high vinyl acetate content.

Example 2

A chlorination modification method of resin with high vinyl acetate content specifically comprises the following specific steps:

s1, adding 100 parts of ethylene-vinyl acetate polymer, 1 part of initiator and 2 parts of dispersant into a reaction kettle, and stirring and mixing uniformly;

s2, introducing chlorine into the reaction kettle in the step S1 for 12min, then heating the reaction kettle, continuing stirring, and stably introducing chlorine for reaction, wherein the amount of chlorine is 4 times of the weight of the ethylene-vinyl acetate, and the chlorination reaction conditions are as follows: the reaction temperature is 120 ℃, the reaction pressure is 0.6MPa, and the reaction time is 4 h;

s3, stopping introducing chlorine after the reaction in the step S2 is finished, preserving heat for 1.5h, then using nitrogen to drive off the residual chlorine in the reaction kettle, cooling to 60 ℃, and reducing the pressure to normal pressure;

and S4, after the temperature and pressure reduction in the step S3 is finished, taking out the sample, and naturally cooling to obtain the resin with high vinyl acetate content.

Example 3

A chlorination modification method of resin with high vinyl acetate content specifically comprises the following specific steps:

s1, adding 100 parts of ethylene-vinyl acetate polymer, 12 parts of vinyl acetate monomer, 2 parts of initiator and 1 part of dispersant into a reaction kettle, and stirring and mixing uniformly;

s2, introducing chlorine gas into the reaction kettle in the step S1 for 15min, then heating the reaction kettle, continuing stirring, and stably introducing the chlorine gas for reaction, wherein the amount of the chlorine gas is 3 times of the weight of the ethylene-vinyl acetate, and the chlorination reaction conditions are as follows: the reaction temperature is 140 ℃, the reaction pressure is 0.8MPa, and the reaction time is 3 h;

s3, stopping introducing chlorine after the reaction in the step S2 is finished, preserving heat for 1h, removing residual chlorine in the reaction kettle by using nitrogen, cooling to 70 ℃, and reducing the pressure to normal pressure;

and S4, after the temperature and pressure reduction in the step S3 is finished, taking out the sample, and naturally cooling to obtain the resin with high vinyl acetate content.

Comparative example 1

A chlorination modification method of resin specifically comprises the following specific steps:

s1, adding 100 parts of ethylene-vinyl acetate polymer, 10 parts of vinyl acetate monomer, 1 part of initiator and 2 parts of dispersant into a reaction kettle, and stirring and mixing uniformly;

s2, introducing chlorine into the reaction kettle in the step S1 for 12min, then heating the reaction kettle, continuing stirring, and stably introducing chlorine for reaction, wherein the amount of chlorine is 4 times of the weight of the ethylene-vinyl acetate, and the chlorination reaction conditions are as follows: the reaction temperature is 120 ℃, the reaction pressure is 0.6MPa, and the reaction time is 4 h;

s3, stopping introducing chlorine after the reaction in the step S2 is finished, preserving heat for 1.5h, then using nitrogen to drive off the residual chlorine in the reaction kettle, cooling to 60 ℃, and reducing the pressure to normal pressure;

and S4, after the temperature and pressure reduction in the step S3 is finished, taking out the sample, and naturally cooling to obtain the resin with high vinyl acetate content.

Comparative example 2

An EAV resin having a conventional vinyl acetate content of 28%.

The EVE resins prepared in examples 1-3 and comparative example 1 and the resin in comparative example 2 were subjected to performance tests according to the method in the Standard GB/T37197-2018 of ethylene-vinyl acetate (EVAC) resin, wherein the vinyl acetate content was measured according to the standard method in GB/T30925-2014 and the heat distortion temperature was measured according to the standard method in GB1633-2000, and the results are shown in Table 1.

TABLE 1 Performance parameters Table

As can be seen from the test results in Table 1, although the vinyl acetate contents of examples 1-3 are higher than those of comparative examples 1 and 2 (ordinary EVA resins), the hardness, crystallinity and heat distortion temperature of the EVA resin after chlorination modification are all equivalent to those of the EVA resin with 28% content, and are not decreased due to the increase of the vinyl acetate content, and the mechanical properties and the melt mass flow rate are improved, which shows that the chlorination modification method of the present invention not only can increase the vinyl acetate content in the EVA resin, but also can improve the comprehensive properties of the resin.

Finally, it should be emphasized that the above-described preferred embodiments of the present invention are merely examples of implementations, rather than limitations, and that many variations and modifications of the invention are possible to those skilled in the art, without departing from the spirit and scope of the invention.