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CN111440257B - Functional ethylene-vinyl acetate copolymer and preparation method thereof - Google Patents

Functional ethylene-vinyl acetate copolymer and preparation method thereof Download PDF

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Publication number
CN111440257B
CN111440257B CN202010287675.4A CN202010287675A CN111440257B CN 111440257 B CN111440257 B CN 111440257B CN 202010287675 A CN202010287675 A CN 202010287675A CN 111440257 B CN111440257 B CN 111440257B
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vinyl acetate
acetate copolymer
ethylene
eva
functional
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CN111440257A (en
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叶书怀
李�诚
张涛
袁凯
吉和信
钟程
苟明明
王亮
赵彦春
丁震东
史慧敏
周虹邑
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Jiangsu Hehe New Material Co ltd
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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F8/00—Chemical modification by after-treatment
    • C08F8/34—Introducing sulfur atoms or sulfur-containing groups
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J123/00—Adhesives based on homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Adhesives based on derivatives of such polymers
    • C09J123/26—Adhesives based on homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Adhesives based on derivatives of such polymers modified by chemical after-treatment
    • C09J123/32—Adhesives based on homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Adhesives based on derivatives of such polymers modified by chemical after-treatment by reaction with compounds containing phosphorus or sulfur
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J7/00—Adhesives in the form of films or foils
    • C09J7/10—Adhesives in the form of films or foils without carriers
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J7/00—Adhesives in the form of films or foils
    • C09J7/30—Adhesives in the form of films or foils characterised by the adhesive composition
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J2423/00—Presence of polyolefin
    • C09J2423/04—Presence of homo or copolymers of ethene
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/50—Photovoltaic [PV] energy

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Health & Medical Sciences (AREA)
  • Medicinal Chemistry (AREA)
  • Polymers & Plastics (AREA)
  • Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)

Abstract

The invention discloses a functional ethylene-vinyl acetate copolymer, which is a mercapto-grafted ethylene-vinyl acetate copolymer, wherein the number average molecular weight is 3000-80000 g/mol, and the mercapto content is 5-800 mmol/100g. The preparation method comprises the following steps: (1) Mixing ethylene-vinyl acetate copolymer, sodium alkoxide and an organic solvent A, then carrying out ester exchange reaction for a period of time, adding water for hydrolysis reaction, and carrying out post-treatment to obtain partially hydrolyzed EVA; (2) Mixing partially hydrolyzed EVA, a sulfhydryl-containing compound and an organic solvent B, carrying out esterification reaction at reflux temperature, and carrying out post-treatment to obtain the functional ethylene-vinyl acetate copolymer. The functional ethylene-vinyl acetate copolymer disclosed by the invention has a proper sulfydryl grafting rate, and particularly has an excellent bonding effect on materials which contain unsaturated double bonds and have low surface polarity, such as natural rubber, styrene butadiene rubber and the like.

Description

Functional ethylene-vinyl acetate copolymer and preparation method thereof
Technical Field
The invention relates to the technical field of ethylene-vinyl acetate copolymers, in particular to a functional ethylene-vinyl acetate copolymer and a preparation method thereof.
Background
Ethylene-vinyl acetate copolymer (EVA) is widely used in the field of adhesives due to its low cost and wide temperature range of application. Because of containing vinyl acetate copolymer chain segments, EVA has the advantages of low glass transition temperature, strong formula applicability, obvious bonding effect on the surface of a strong-polarity substrate and the like, and is widely used in the fields of hot melt adhesives and the like.
However, EVA hotmelt adhesives also have significant disadvantages: mainly has lower bonding strength, is not resistant to high and low temperature, and is not resistant to fatty oil and the like. Which is determined by the chemical characteristics and the physical structure of the components of the EVA hot melt adhesive. The EVA resin is a thermoplastic resin, and has a low softening point and limited high and low temperature resistance. The main auxiliary material, namely the tackifier, has the function of reducing the melt viscosity so as to improve the wetting capacity and the initial adhesion performance to an adherend, and most of the materials are polymers with relatively low molecular mass and are also not resistant to high and low temperatures. The EVA hot melt adhesive structure main body is formed by blending high polymer materials with different performances, and the colloid has limited heat resistance, low thermal stability and poor low-temperature performance during preparation and use; and the coating is not suitable for large-area coating and bonding because the skinning is easy to generate. When the specific external conditions of the object to be used are changed continuously or the quality or quantity of the basic interface of the object to be processed is changed, the quality problem that the bonding effect does not reach the standard often occurs. Therefore, the EVA alone used as the base polymer can not meet the technical requirements of industrial development after being subjected to a certain range of proportion adjustment, and can be adapted to wider application fields only by being modified.
At present, graft modification of EVA base polymers is the main direction of development in recent years. The modified EVA hot melt adhesive is prepared by reacting some active molecules with functional groups on an EVA main chain by a chemical method to generate modified EVA resin with special performance, and then blending the modified EVA resin with a tackifier, a filler and the like.
Yan Jinjie (Yan Jinjie, research on maleic anhydride grafted modified EVA Hot melt adhesive [ J ] Chinese Adhesives, 2005, (5): 18-21.) A hot melt adhesive is prepared by grafting maleic anhydride onto EVA by using organic peroxide as an initiator by a melt grafting method, and the hot melt adhesive also has good results on bonding of metals, nylon and wood.
Chinese patent publication No. CN 1800287A discloses the preparation of a silane-modified EVA hot melt adhesive composition, wherein active silane groups are grafted on the macromolecular chain of EVA resin by a reactive extrusion or melt reaction method, and the heat resistance and adhesive properties of the hot melt adhesive system are improved by further crosslinking reaction of the silane groups.
However, the modified EVA hot melt adhesive prepared by the method has unsatisfactory bonding effect on materials which contain unsaturated double bonds and have lower surface polarity, such as natural rubber, styrene butadiene rubber and the like.
Disclosure of Invention
The invention discloses a functional ethylene-vinyl acetate copolymer and a preparation method thereof aiming at the problems in the prior art, wherein the functional ethylene-vinyl acetate copolymer has a proper sulfydryl grafting rate, and particularly has an excellent bonding effect on materials which contain unsaturated double bonds and have lower surface polarity, such as natural rubber, styrene butadiene rubber and the like.
The specific technical scheme is as follows:
a functional ethylene-vinyl acetate copolymer is a mercapto-grafted ethylene-vinyl acetate copolymer, the number average molecular weight is 3000-80000 g/mol, and the mercapto content is 5-400 mmol/100g.
The mercapto group chemically modified and grafted on the surface of the functional ethylene-vinyl acetate copolymer disclosed by the invention can obviously improve the bonding strength of materials which contain unsaturated double bonds and have lower surface polarity, such as EVA, natural rubber, styrene butadiene rubber and the like.
Preferably, the number average molecular weight of the functional ethylene-vinyl acetate copolymer is 5000-70000 g/mol, and the content of sulfydryl is 210-620 mmol/100g.
Tests show that the functional EVA with the optimized parameters has higher bonding strength with materials which contain unsaturated double bonds and have lower surface polarity, such as natural rubber, styrene butadiene rubber and the like.
More preferably, the number average molecular weight of the functional ethylene-vinyl acetate copolymer is 35000-37000 g/mol, and the content of sulfhydryl group is 220-510 mmol/100g.
Tests show that the functional EVA under the further optimized parameters has higher bonding strength with materials which contain unsaturated double bonds and have lower surface polarity, such as natural rubber, styrene butadiene rubber and the like, and the interfacial bonding strength is close to the cohesive strength of the EVA body, so that the comprehensive performance is better.
Most preferably, the number average molecular weight of the functional ethylene-vinyl acetate copolymer is 35000-37000 g/mol, and the mercapto content is 430-510 mmol/100g.
Tests show that the functional EVA with the most preferable parameters has the highest shearing strength and 180-degree peel strength when the interfacial bonding strength between the functional EVA and materials which contain unsaturated double bonds and have low surface polarity, such as natural rubber, styrene butadiene rubber and the like, is close to the cohesive strength of an EVA body.
The invention also discloses a preparation method of the functional ethylene-vinyl acetate copolymer, which comprises the following steps:
(1) Mixing ethylene-vinyl acetate copolymer, sodium alkoxide and an organic solvent A, carrying out ester exchange reaction for a period of time, adding water for hydrolysis reaction, and carrying out post-treatment to obtain partially hydrolyzed EVA, wherein the hydrolysis degree of vinyl acetate groups in the partially hydrolyzed EVA is 5-80%;
(2) Mixing the partially hydrolyzed EVA, the mercapto compound and the organic solvent B prepared in the step (1), carrying out esterification reaction at a reflux temperature, and carrying out post-treatment to obtain the functional ethylene-vinyl acetate copolymer.
The method takes EVA as a raw material, firstly hydrolyzes ester groups in the EVA into hydroxyl groups through ester exchange reaction and hydrolysis reaction, then carries out esterification reaction by utilizing the hydroxyl groups and carboxyl groups in a sulfhydryl-containing compound, and finally grafts sulfhydryl groups on the EVA. The key point of the preparation process is that ethylene-vinyl acetate copolymer raw materials with proper molecular weight and VA content are screened, the hydrolysis degree of the ethylene-vinyl acetate copolymer in the first step is controlled, and functional EVA with proper mercapto grafting rate can be prepared by controlling the process parameters in a proper range, and has excellent bonding effect on materials which contain unsaturated double bonds and have lower surface polarity, such as natural rubber, styrene butadiene rubber and the like.
Tests show that the hydrolysis degree is low, the mercapto content of a final product obtained by the next esterification reaction with a mercapto compound is influenced, the interface bonding strength of the final product is poor due to the low mercapto content, the hydrolysis degree is high, the final product with high mercapto content can be obtained, and the bulk strength of the final product is influenced.
The hydrolysis degree in the present invention refers to the degree of hydrolysis of part of the vinyl acetate groups of EVA after hydrolysis reaction and further formation of hydroxyl groups.
In the step (1):
preferably, the number average molecular weight of the ethylene-vinyl acetate copolymer is 3000-80000 g/mol, and the weight percentage content of vinyl acetate groups is 10-50%; more preferably, the number average molecular weight of the ethylene-vinyl acetate copolymer is 5000-70000 g/mol, and the weight percentage content of vinyl acetate is 15-40%.
Tests show that the ethylene-vinyl acetate copolymer has lower number average molecular weight, the final product has better interface bonding performance, but has poorer body strength and higher molecular weight, and the glue layer has excellent body strength but poorer interface bonding performance.
Tests also show that in the ethylene-vinyl acetate copolymer, the weight percentage content of vinyl acetate is higher, the bonding interface strength is higher, but the adhesive layer bulk strength is lower; if the vinyl acetate group content is low, the adhesive layer bulk strength is high, but the adhesive interface strength is reduced.
More preferably, the number average molecular weight of the ethylene-vinyl acetate copolymer is 35000-37000 g/mol, and the weight percentage content of the vinyl acetate is 25-30%.
Preferably, the sodium alkoxide is selected from sodium methoxide and/or sodium ethoxide. Experiments show that if sodium alkoxide is replaced by common alkaline substances such as sodium hydroxide and the like, the mercapto grafting rate is greatly reduced.
The organic solvent A is selected from good solvents of ethylene-vinyl acetate copolymer, and is specifically selected from at least one of benzene, toluene, petroleum ether, dichloromethane and chloroform; toluene and dichloromethane are preferred, wherein toluene has good solubility to medium-low molecular weight EVA, and dichloromethane has good solubility to high molecular weight EVA.
Preferably, the first and second electrodes are formed of a metal,
the molar ratio of vinyl acetate groups to sodium alcoholates in the ethylene-vinyl acetate copolymer is 1:0.05 to 2; more preferably 1:0.6 to 1.1; more preferably 1:1.1.
in the organic solvent A, the concentration of the ethylene-vinyl acetate copolymer is 0.01-0.5 g/mL; more preferably 0.1 to 0.4g/mL; still more preferably 0.33g/mL.
Preferably, the ester exchange reaction is carried out at the reaction temperature of 10-30 ℃ for 0.5-6 hours; further preferably, the temperature is 20 ℃ and the time is 2 to 4 hours.
Preferably, the first and second electrodes are formed of a metal,
in the hydrolysis reaction, the molar ratio of the added water to the sodium alkoxide is 1-3: 1; more preferably 1.1 to 2:1; still more preferably 1.1:1.
the temperature of the hydrolysis reaction is 20-60 ℃, and the time is 0.5-12 h; further preferably, the temperature is 30 to 50 ℃ and the time is 2 to 10 hours.
In the hydrolysis reaction, proper vinyl acetate group can be converted into hydroxyl by controlling the hydrolysis degree of the ethylene-vinyl acetate copolymer, so that preparation is provided for the next reaction with the sulfhydryl compound. If the amount of vinyl acetate groups converted into hydroxyl groups is too small, the mercapto content of the final product is affected, resulting in poor interfacial bond strength of the adhesive layer, and if the amount converted into hydroxyl groups is too large, the cohesive strength of the adhesive layer is affected.
Preferably, in the partially hydrolyzed EVA, the hydrolysis degree of the vinyl acetate group is 52 to 80%; further preferably, the degree of hydrolysis is 75 to 80%; a further preferred degree of hydrolysis is from 78 to 80%.
The post-treatment comprises washing, and drying the organic layer.
In the step (2):
preferably, the thiol-containing compound is selected from thioglycolic acid and/or mercaptopropionic acid; further preferred is thioglycolic acid. Tests show that compared with mercaptopropionic acid, the mercapto compound is selected from mercaptoacetic acid, and under the condition that other process conditions are not changed, the shear strength and 180-degree peel strength of the finally prepared functional EVA are obviously improved.
The organic solvent B is also selected from good solvents of ethylene-vinyl acetate copolymer, and is specifically selected from at least one of benzene, toluene, petroleum ether, dichloromethane and chloroform; toluene and dichloromethane are preferred.
The molar ratio of the mercapto compound to the vinyl acetate group in the ethylene-vinyl acetate copolymer is 0.2-5: 1; more preferably 0.42 to 0.67:1.
in the organic solvent B, the concentration of the sulfhydryl-containing compound is 0.05-0.6 g/mL; more preferably 0.063 to 0.16g/mL.
The work-up comprises cooling to room temperature, addition of methanol/ethanol, settling of the product, filtration and drying.
Most preferably:
in the step (1):
the number average molecular weight of the ethylene-vinyl acetate copolymer is 35000-37000 g/mol;
the molar ratio of vinyl acetate groups to sodium alcoholates in the ethylene-vinyl acetate copolymer is 1:1.1;
the hydrolysis reaction is carried out, and the molar ratio of the added water to the sodium alkoxide is 1.1:1;
in the partially hydrolyzed EVA, the hydrolysis degree of the vinyl acetate group is 78-80%;
in the step (2):
the thiol-containing compound is selected from thioglycolic acid.
Under the more preferable process parameters, the interface bonding strength of the prepared functional EVA with materials containing unsaturated double bonds and having low surface polarity, such as natural rubber, styrene-butadiene rubber and the like, is close to the cohesive strength of an EVA body, and the shear strength and 180-degree peel strength of the functional EVA are both highest.
Compared with the prior art, the invention has the beneficial effects that:
the invention discloses a functional EVA and a preparation method thereof, wherein the functional EVA with a proper mercapto grafting rate is prepared by screening an ethylene-vinyl acetate copolymer raw material with a proper molecular weight and VA content and controlling the hydrolysis degree of the EVA raw material in the first hydrolysis reaction, and has an excellent bonding effect on materials which contain unsaturated double bonds and have lower surface polarity, such as natural rubber, styrene butadiene rubber and the like.
Detailed Description
Example 1
Adding 50g of EVA (Japanese Tosoh EVA625, the number average molecular weight is 68000-70000 g/mol, the VA content is 15%), 150mL of toluene and 10.36g of sodium methoxide (0.19mol, the molar ratio of the VA group to the sodium methoxide is 1.1), controlling the reaction temperature at 20 ℃ to perform ester exchange reaction for 2 hours, adding 3.76g of water (0.21 mol) into the system to perform hydrolysis reaction at 40 ℃ for 2 hours, cooling, washing with water, taking an organic layer and drying to obtain the partially hydrolyzed EVA (the hydrolysis degree is 80%). This was dissolved in 200mL of toluene, and 12.83g of thioglycolic acid (0.14 mol, molar ratio of thioglycolic acid to VA group 0.67.
The functional EVA prepared by the embodiment has the number average molecular weight of 68000-70000 g/mol and the sulfhydryl content of 210mmol/100g.
Example 2
50g of EVA (Taiwan 7760H, number average molecular weight of 35000-37000 g/mol, VA content 28%), 150mL of toluene and 19.34g of sodium methoxide (0.36mol, molar ratio of VA group to sodium methoxide 1.1), the transesterification reaction was carried out at 20 ℃ with the reaction temperature controlled, reacting for 2 hours, adding 7.13g (0.4 mol) of water into the system for hydrolysis reaction at 40 ℃ for 2 hours, cooling, washing, taking an organic layer and drying to obtain partially hydrolyzed EVA (the hydrolysis degree is 78%). This was dissolved in 200mL of toluene, and 23.36g of thioglycolic acid (0.25 mol, molar ratio of thioglycolic acid to VA group 0.63.
The number average molecular weight of the functional EVA prepared by the embodiment is 35000-37000 g/mol, and the content of sulfydryl is 430mmol/100g.
Example 3
Adding 50g of EVA (Belgium Shi Aike Sen chemical UL5540, the number average molecular weight is 5000-6000 g/mol, the VA content is 40%), 150mL of toluene and 27.63g of sodium methoxide (0.51mol, the molar ratio of the VA group to the sodium methoxide is 1.1), controlling the reaction temperature to carry out transesterification reaction at 20 ℃ for 2 hours, adding 10.13g (0.56 mol) of water into the system to carry out hydrolysis reaction at 40 ℃, reacting for 2 hours, cooling, washing with water, taking an organic layer and drying to obtain the partially hydrolyzed EVA (the hydrolysis degree is 75%). This was dissolved in 200mL of toluene, and 32.09g of thioglycolic acid (0.35 mol, molar ratio of thioglycolic acid to VA group 0.62.
The functional EVA prepared by the embodiment has the number average molecular weight of 5000-6000 g/mol and the mercapto content of 620mmol/100g.
Example 4
50g of EVA (Taiwan 7760H, number average molecular weight of 35000-37000 g/mol, VA content 28%), 150mL of toluene and 19.34g of sodium methoxide (0.36mol, molar ratio of VA group to sodium methoxide 1.1), the transesterification reaction was carried out at 20 ℃ with the reaction temperature controlled, reacting for 4 hours, adding 7.13g (0.4 mol) of water into the system for hydrolysis reaction at 40 ℃ for 4 hours, cooling, washing, taking an organic layer and drying to obtain the partially hydrolyzed EVA (with the hydrolysis degree of 80%). The resulting mixture was dissolved in 200mL of toluene, 23.36g (0.25 mol) of mercaptoacetic acid was added thereto, the mixture was refluxed at 110 ℃ to conduct esterification, and after reacting for 4 hours, the temperature was lowered to room temperature, 200mL of methanol was added, and the product was precipitated, filtered and dried to obtain the final product.
The functional EVA prepared in this example has a number average molecular weight of 35000-37000 g/mol, and a mercapto group content of 510mmol/100g.
Example 5
50g of EVA (Taiwan 7760H, the number-average molecular weight of 35000-37000 g/mol, VA content 28%), 150mL of toluene and 10.6g of sodium methoxide (0.20mol, molar ratio of VA group to sodium methoxide 1: 0.6), the transesterification reaction was carried out at 20 ℃ while controlling the reaction temperature, reacting for 2 hours, adding 7.13g (0.4 mol) of water into the system for hydrolysis reaction at 40 ℃ for 2 hours, cooling, washing, taking an organic layer and drying to obtain partially hydrolyzed EVA (the hydrolysis degree is 52%). This was dissolved in 200mL of toluene, and 12.55g of thioglycolic acid (0.14 mol, molar ratio of thioglycolic acid to VA group 0.42.
The functional EVA prepared by the embodiment has the number average molecular weight of 35000-37000 g/mol and the sulfhydryl content of 220mmol/100g.
Example 6
50g of EVA (Taiwan 7760H, number average molecular weight of 35000-37000 g/mol, VA content 28%), 150mL of toluene and 19.34g of sodium methoxide (0.36mol, molar ratio of VA group to sodium methoxide 1.1), the transesterification reaction was carried out at 20 ℃ with the reaction temperature controlled, reacting for 2 hours, adding 7.13g (0.4 mol) of water into the system for hydrolysis reaction at 40 ℃ for 2 hours, cooling, washing, taking an organic layer and drying to obtain partially hydrolyzed EVA (the hydrolysis degree is 78%). The resulting mixture was dissolved in 200mL of toluene, 26.5g (0.25 mol) of mercaptopropionic acid was added, the esterification reaction was carried out at 110 ℃ under reflux, the reaction was allowed to cool to room temperature after 2 hours, 200mL of methanol was added, the product was precipitated, filtered and dried to obtain the final product.
The number average molecular weight of the functional EVA prepared by the embodiment is 35000-37000 g/mol, and the content of sulfydryl is 330mmol/100g.
Comparative example 1
The Japanese east Cao EVA625 with number average molecular weight of 68000-70000 g/mol and VA content of 15% was selected as comparative example 1.
Comparative example 2
Selecting Taiwan taiwan tai plast 7760H, number average molecular weight of 35000-37000 g/mol, the VA content of 28% is used as comparative example 2.
And (3) performance testing:
the sample preparation method comprises the following steps: the functional EVA prepared in the embodiment is pressed into a glue film with the thickness of 300 micrometers, attached between two natural rubbers, heated to 180 ℃ and pressed for 60 seconds, and then tested. The specific test conditions/standards, as well as the test data, are listed in table 1 below.
TABLE 1
Figure GDA0004040371060000101

Claims (6)

1. A functional ethylene-vinyl acetate copolymer used for bonding materials containing unsaturated double bonds and having low surface polarity is a sulfydryl grafted ethylene-vinyl acetate copolymer, and is characterized in that the number average molecular weight of the functional ethylene-vinyl acetate copolymer is 35000-37000 g/mol, and the sulfydryl content is 220-510 mmol/100g;
the material containing unsaturated double bonds and low surface polarity is selected from natural rubber and/or styrene-butadiene rubber;
the preparation method of the functional ethylene-vinyl acetate copolymer comprises the following steps:
(1) Mixing ethylene-vinyl acetate copolymer, sodium alkoxide and an organic solvent A, carrying out ester exchange reaction for a period of time, adding water for hydrolysis reaction, and carrying out post-treatment to obtain partially hydrolyzed EVA, wherein the hydrolysis degree of vinyl acetate groups in the partially hydrolyzed EVA is 78-80%;
the number average molecular weight of the ethylene-vinyl acetate copolymer is 35000-37000 g/mol, and the weight percentage content of the vinyl acetate is 25-30%;
the molar ratio of vinyl acetate groups to sodium alcoholates in the ethylene-vinyl acetate copolymer is 1:0.6 to 1.1;
in the hydrolysis reaction, the molar ratio of the added water to the sodium alkoxide is 1.1-2: 1;
(2) Mixing the partially hydrolyzed EVA, the mercapto compound and the organic solvent B prepared in the step (1), carrying out esterification reaction at a reflux temperature, and carrying out post-treatment to obtain the functional ethylene-vinyl acetate copolymer.
2. The functional ethylene-vinyl acetate copolymer according to claim 1, wherein in step (1):
the sodium alkoxide is selected from sodium methoxide and/or sodium ethoxide;
the organic solvent A is selected from at least one of benzene, toluene, petroleum ether, dichloromethane and chloroform;
in the organic solvent A, the concentration of the ethylene-vinyl acetate copolymer is 0.01-0.5 g/mL.
3. The functional ethylene-vinyl acetate copolymer according to claim 1, wherein in step (1):
the ester exchange reaction is carried out at the reaction temperature of 10-30 ℃ for 0.5-6 hours.
4. The functional ethylene-vinyl acetate copolymer according to claim 1, wherein in step (1):
the temperature of the hydrolysis reaction is 20-60 ℃, and the time is 0.5-12 h;
the post-treatment comprises washing, and drying the organic layer.
5. The functional ethylene-vinyl acetate copolymer according to claim 1, wherein in the step (2):
the mercapto compound is selected from thioglycolic acid and/or mercaptopropionic acid;
the organic solvent B is at least one selected from benzene, toluene, petroleum ether, dichloromethane and chloroform;
the molar ratio of the mercapto compound to the vinyl acetate group in the ethylene-vinyl acetate copolymer is 0.2-5: 1;
in the organic solvent B, the concentration of the sulfhydryl-containing compound is 0.05-0.6 g/mL.
6. The functional ethylene-vinyl acetate copolymer according to claim 1, wherein in the step (2):
the work-up comprises cooling to room temperature, addition of methanol and/or ethanol, settling of the product, filtration and drying.
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