Preparation method and application of ethylene-vinyl acetate copolymer

Abstract

The invention provides an ethylene-vinyl acetate copolymer preparation method, which comprises: 1) carrying out a copolymerization reaction on ethylene and vinyl acetate at a reaction pressure of 200-400 MPa and a reaction temperature of 150-300 DEG C to obtain a reaction product; and 2) depressurizing and cooling the reaction product to provide the required ethylene-vinyl acetate copolymer. The invention also provides the ethylene-vinyl acetate copolymer and application thereof in the fields of foaming materials, cable materials, coating materials, photovoltaic materials or film materials. According to the preparation method and application of the ethylene-vinyl acetate copolymer provided by the invention, the obtained ethylene-vinyl acetate copolymer has excellent heat resistance and mechanical properties, is suitable for being applied in a high-temperature environment, and can be widely applied to the fields of foaming materials, cable materials, coating materials, photovoltaic materials or film materials.

Description

Technical Field

[0001] The present invention belongs to the technical field of polymer material preparation, and relates to a preparation method of ethylene-vinyl acetate copolymer and application thereof, and specifically relates to a preparation method of ethylene-vinyl acetate copolymer (EVA) and application thereof in the fields of foaming materials, cable materials, coating materials, photovoltaic materials or thin film materials. Background Art

[0002] Ethylene-vinyl acetate copolymer (EVA) has been widely used in various industrial and consumer fields due to its good flexibility, transparency and heat resistance. The physical and chemical properties of EVA can be changed by adjusting the content of vinyl acetate (VA). For example, when the VA content is high, the material is softer and more transparent; when the VA content is low, the rigidity and heat resistance of the material are enhanced. The traditional EVA preparation process is carried out at a relatively low pressure and temperature, resulting in limited product performance improvement. CN103626910A discloses a solid ethylene-vinyl acetate copolymer with a VA weight percentage of more than 70% prepared by a solution polymerization process and a preparation method thereof. However, the preparation of EVA products with excellent performance still requires the use of free radical polymerization reaction process technology. Summary of the invention

[0003] In view of the characteristics of the prior art described above, the purpose of the present invention is to provide a method for preparing ethylene-vinyl acetate copolymer and its application, which can make the molecular structure of EVA copolymer more uniform and significantly improve the performance, and is suitable for use in foaming materials, cable sheaths, coatings, photovoltaic encapsulation films and various industrial films.

[0004] To achieve the above object and other related objects, the present invention provides a method for preparing an ethylene-vinyl acetate copolymer in a first aspect, comprising the following steps:

[0005] 1) copolymerizing ethylene and vinyl acetate at a reaction pressure of 200-400 MPa and a reaction temperature of 150-300° C. to obtain a reaction product;

[0006] 2) The reaction product is depressurized and cooled to provide the desired ethylene-vinyl acetate copolymer.

[0007] The second aspect of the present invention provides an ethylene-vinyl acetate copolymer prepared by the above method.

[0008] The third aspect of the present invention provides the use of the above-mentioned ethylene-vinyl acetate copolymer in the fields of foaming materials, cable materials, coating materials, photovoltaic materials or film materials.

[0009] As described above, the present invention provides a method for preparing an ethylene-vinyl acetate copolymer and its application. By adjusting the speed of the reactor under high pressure and high temperature conditions, an ethylene-vinyl acetate copolymer (EVA) containing vinyl acetate (VA) can be synthesized in a free radical-initiated manner through a specific ratio of ethylene to vinyl acetate. The ethylene-vinyl acetate copolymer obtained by this method has a more uniform molecular structure, significantly improved performance, excellent heat resistance and mechanical properties, is suitable for applications in high temperature environments, and can be widely used in the fields of foaming materials, cable materials, coating materials, photovoltaic materials or thin film materials. DETAILED DESCRIPTION

[0010] The following detailed description specifically discloses a method for preparing an ethylene-vinyl acetate copolymer of the present application and its application. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there may be cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structure are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the following description is provided for those skilled in the art to fully understand the present application and is not intended to limit the subject matter described in the claims.

[0011] "Scope" disclosed in the present application is limited in the form of lower limit and upper limit, and a given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a special range. The scope limited in this way can be including end values ​​or not including end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a scope. For example, if the scope of 60-120 and 80-110 is listed for a specific parameter, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are listed, the following scope can be all expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present application, unless otherwise specified, the numerical range "ab" represents the abbreviation of any real number combination between a and b, wherein a and b are real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0012] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0013] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0014] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (1) and (2), which means that the method may include steps (1) and (2) performed sequentially, or may include steps (2) and (1) performed sequentially. For example, the method may further include step (3), which means that step (3) may be added to the method in any order, for example, the method may include steps (1), (2) and (3), or may include steps (1), (3) and (2), or may include steps (3), (2) and (1), etc.

[0015] If there is no special explanation, the "include" and "comprising" mentioned in this application are open-ended or closed-ended. For example, the "include" and "comprising" may mean that other components not listed may also be included or only the listed components may be included or only the listed components may be included.

[0016] If not specifically stated, in this application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, any of the following conditions satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0017] The first aspect of the present invention provides a method for preparing an ethylene-vinyl acetate copolymer, comprising the following steps:

[0018] 1) copolymerizing ethylene and vinyl acetate at a reaction pressure of 200-400 MPa and a reaction temperature of 150-300° C. to obtain a reaction product;

[0019] 2) The reaction product is depressurized and cooled to provide the desired ethylene-vinyl acetate copolymer.

[0020] In the above step 1), the weight ratio of ethylene to vinyl acetate is 5-100:0-95, specifically 55-100:0-45, 5-55:45-95, preferably 55-100:0-45, more preferably 60-90:10-40.

[0021] In the above step 1), an initiator is further added to the copolymerization reaction, and the initiator is selected from at least one of azobisisobutyronitrile, di(2-ethylhexyl) peroxydicarbonate, tert-butyl peroxypivalate, tert-butyl peroxy-2-ethylhexanoate, tert-butyl peroxy-3,5,5-trimethylhexanoate, di-tert-butyl peroxide or benzoyl peroxide.

[0022] The above copolymerization reaction is a copolymerization reaction initiated by free radicals, and an initiator needs to be added.

[0023] In one embodiment, the weight ratio of the initiator to ethylene added is 0-0.009:1.

[0024] In the above step 1), the copolymerization reaction is carried out in a reactor, and the stirring speed in the reactor is 500-1000 rpm, such as 500-600 rpm, 600-800 rpm, 800-1000 rpm, preferably 600-800 rpm.

[0025] In the above step 1), the reaction time of the copolymerization reaction is 30-120 min, specifically 30-60 min, 60-90 min, 90-120 min, preferably 60-90 min.

[0026] In the above step 1), the reaction pressure of the copolymerization reaction may be 200-250 MPa, 250-350 MPa, 350-400 MPa, preferably 250-350 MPa.

[0027] In the above step 1), the reaction temperature of the copolymerization reaction can be 150-200°C, 200-250°C, 250-300°C, preferably 200-250°C.

[0028] In the above step 2), the pressure is reduced to the atmospheric pressure at the location of the copolymerization reaction.

[0029] In the above step 2), the cooling to room temperature is 20-30°C.

[0030] The second aspect of the present invention provides an ethylene-vinyl acetate copolymer prepared by the above method.

[0031] In the above copolymer, the ratio of the weight average molecular weight Mw to the number average molecular weight Mn of the ethylene-vinyl acetate copolymer is 1.8-12.1.

[0032] The third aspect of the present invention provides the use of the above-mentioned ethylene-vinyl acetate copolymer in the fields of foaming materials, cable materials, coating materials, photovoltaic materials or film materials.

[0033] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0034] In the following examples, unless otherwise specified, raw materials or processing techniques are conventional commercially available raw materials or conventional processing techniques in the art.

[0035] Example 1

[0036] In a 2L autoclave, 180g of ethylene monomer and 20g of vinyl acetate monomer (VA content of 10wt%) were added. 1g of di(2-ethylhexyl) peroxydicarbonate was added as an initiator, the reaction temperature was set to 220°C, the pressure was 300MPa, the stirring speed of the autoclave was 600rpm, and the reaction time was 60min. After the reaction was completed, the pressure was reduced and the reaction was cooled to obtain an ethylene-vinyl acetate (EVA) copolymer sample 1 with Mw / Mn=6.4.

[0037] Ethylene-vinyl acetate copolymer sample 1 can be used for photovoltaic encapsulation film, showing excellent volume resistivity and water absorption properties.

[0038] Example 2

[0039] In a 2L autoclave, add 160g of ethylene monomer and 40g of vinyl acetate monomer (mixed in a weight ratio of 8:2, i.e., VA content of 20wt%). Then add tert-butyl peroxypivalate as an initiator, and the weight ratio of the initiator to the ethylene is 0.0005:1. The reaction temperature is set to 250°C, the pressure is 350MPa, the stirring speed of the autoclave is 700rpm, and the reaction time is 90min. After the reaction is completed, reduce the pressure and cool to obtain an ethylene-vinyl acetate copolymer sample 2 with Mw / Mn=3.5.

[0040] Ethylene-vinyl acetate copolymer sample 2 can be used in hot melt adhesives and has excellent flexibility and adhesion properties.

[0041] Example 3

[0042] In a 2L autoclave, add 140g of ethylene monomer and 60g of vinyl acetate monomer (mixed in a weight ratio of 7:3, i.e., VA content of 30wt%). Then add tert-butyl peroxy 2-ethylhexanoate as an initiator, and the weight ratio of the initiator to the ethylene is 0.0008:1. The reaction temperature is set to 230°C, the pressure is 250MPa, the stirring speed of the autoclave is 800rpm, and the reaction time is 45min. After the reaction is completed, reduce the pressure and cool to obtain ethylene-vinyl acetate copolymer sample 3 with Mw / Mn=4.4.

[0043] Ethylene-vinyl acetate copolymer sample 3 can be used for cable sheath, and has good heat resistance and impact resistance. It can also be used for photovoltaic encapsulation film, and exhibits excellent volume resistivity and water absorption performance.

[0044] Example 4

[0045] In a 2L autoclave, add 120g of ethylene monomer and 80g of vinyl acetate monomer (mixed in a weight ratio of 6:4, i.e., VA content of 40wt%). Then add tert-butyl peroxy-3,5,5-trimethylhexanoate as an initiator, and the weight ratio of the initiator to the ethylene is 0.001:1. The reaction temperature is set to 180°C, the pressure is 250MPa, the stirring speed of the reactor is 750rpm, and the reaction time is 60min. After the reaction is completed, reduce the pressure and cool to obtain ethylene-vinyl acetate copolymer sample 4 with Mw / Mn=4.4.

[0046] Ethylene-vinyl acetate copolymer sample 4 can be used for foaming materials with good elasticity and durability, and can also be used for hot melt adhesives with excellent flexibility and adhesion properties.

[0047] Example 5

[0048] In a 2L autoclave, add 180g of ethylene monomer and 20g of vinyl acetate monomer (mixed in a weight ratio of 9:1, i.e., VA content of 10wt%). Then add di-tert-butyl peroxide as an initiator, and the weight ratio of the initiator to the ethylene is 0.0003:1. The reaction temperature is set to 230°C, the pressure is 300MPa, the stirring speed of the autoclave is 900rpm, and the reaction time is 90min. After the reaction is completed, reduce the pressure and cool to obtain an ethylene-vinyl acetate copolymer sample 5 with Mw / Mn=3.1.

[0049] Ethylene-vinyl acetate copolymer sample 5 can be used for coating materials and has good water resistance and abrasion resistance.

[0050] Example 6

[0051] In a 2L autoclave, add 190g of ethylene monomer and 10g of vinyl acetate monomer (i.e., VA content 5wt%) and mix. Then add 1g of tert-butyl peroxy 2-ethylhexanoate as an initiator. The reaction temperature is set to 240°C, the pressure is 250MPa, the stirring speed of the autoclave is 750rpm, and the reaction time is 60min. After the reaction is completed, the pressure is reduced and cooled to obtain an ethylene-vinyl acetate copolymer sample 6 with Mw / Mn=6.5.

[0052] Ethylene-vinyl acetate copolymer sample 6 can be used for photovoltaic encapsulation film and has excellent optical transparency.

[0053] Example 7

[0054] In a 2L autoclave, add 120g of ethylene monomer and 80g of vinyl acetate monomer (mixed in a weight ratio of 6:4, i.e., VA content of 40wt%). Then add tert-butyl peroxy 2-ethylhexanoate as an initiator, and the weight ratio of the initiator to the ethylene is 0.0009:1. The reaction temperature is set to 210°C, the pressure is 300MPa, the stirring speed of the autoclave is 700rpm, and the reaction time is 90min. After the reaction is completed, reduce the pressure and cool to obtain an ethylene-vinyl acetate copolymer sample 7 with Mw / Mn=5.

[0055] Ethylene-vinyl acetate copolymer sample 7 can be used for sole foaming material, and has excellent resilience and wear resistance. And its density is 0.969g / cm 3 , the density value is relatively large. , It can also be used in hot melt adhesives, with excellent flexibility and adhesion properties.

[0056] Example 8

[0057] In a 2L autoclave, 180g of ethylene monomer and 20g of vinyl acetate monomer (mixed in a weight ratio of 9:1, i.e., VA content of 10wt%) were added, and then tert-butyl peroxy-3,5,5-trimethylhexanoate was added as an initiator, and the weight ratio of the initiator to the ethylene added was 0.0005:1. The reaction temperature was set at 270°C, the pressure was 350MPa, the stirring speed of the autoclave was 900rpm, and the reaction time was 60min. After the reaction was completed, the pressure was reduced and cooled to obtain an ethylene-vinyl acetate copolymer sample 8 with Mw / Mn=3.5.

[0058] Ethylene-vinyl acetate copolymer sample 8 can be used for industrial coatings and has good anti-aging properties.

[0059] Example 9

[0060] In a 2L autoclave, 160g of ethylene monomer and 40g of vinyl acetate monomer were added and mixed (i.e., VA content 20wt%). 1g of tert-butyl peroxy 2-ethylhexanoate was added as an initiator. The reaction temperature was set at 200°C, the pressure was 250MPa, the stirring speed of the autoclave was 500rpm, and the reaction time was 45min. After the reaction was completed, an ethylene-vinyl acetate copolymer sample 9 with Mw / Mn=4.1 was obtained.

[0061] Ethylene-vinyl acetate copolymer sample 9 can be used for building films and has good tensile strength and high temperature resistance.

[0062] Example 10

[0063] In a 2L autoclave, 180g of ethylene monomer and 20g of vinyl acetate monomer (VA content 10wt%) were added. 1g of tert-butyl peroxy 2-ethylhexanoate was added as an initiator. The reaction temperature was set to 290°C, the pressure was 300MPa, the stirring speed of the autoclave was 600rpm, and the reaction time was 60min. After the reaction was completed, an ethylene-vinyl acetate copolymer sample 10 with Mw / Mn=4.4 was obtained.

[0064] The ethylene-vinyl acetate copolymer sample 10 can be used as an EVA film material for food packaging.

[0065] Comparative Example 1

[0066] In a 2L autoclave, 80g of ethylene monomer and 20g of vinyl acetate monomer (VA content of 20wt%) were added. 1g of di(2-ethylhexyl) peroxydicarbonate was added as an initiator, the reaction temperature was set to 320°C, the pressure was 300MPa, the stirring speed of the autoclave was 600rpm, and the reaction time was 60min. After the reaction was completed, the pressure was reduced and the reaction was cooled to obtain an ethylene-vinyl acetate (EVA) copolymer comparative sample 1# with Mw / Mn=3.1.

[0067] Comparative Example 2

[0068] In a 2L autoclave, 80g of ethylene monomer and 20g of vinyl acetate monomer (VA content of 20wt%) were added. 1g of di(2-ethylhexyl) peroxydicarbonate was added as an initiator, the reaction temperature was set to 220°C, the pressure was 150MPa, the stirring speed of the autoclave was 600rpm, and the reaction time was 60min. After the reaction was completed, the pressure was reduced and cooled to obtain an ethylene-vinyl acetate (EVA) copolymer comparative sample 2# with Mw / Mn=4.4.

[0069] The specific differences in preparation conditions between the ethylene-vinyl acetate copolymer sample 1 in the above-mentioned Example 1 and the ethylene-vinyl acetate copolymer comparison samples in Comparative Examples 1-2 are shown in Table 1.

[0070] Table 1

[0071]

[0072] Comparative test example 1

[0073] The ethylene-vinyl acetate copolymer sample 1 in Example 1 and the ethylene-vinyl acetate copolymer comparison samples in Comparative Examples 1-2 were used as photovoltaic encapsulation films, and volume resistivity tests and water absorption performance tests were performed respectively. The specific test results are shown in Table 2 below.

[0074] Table 2

[0075] sample <![CDATA[Volume resistivity performance index (Ω·cm × 10 14 )]]> Water absorption performance index 24h (%) Example 1 2.94 0.128 Comparative Example 1 3.61 0.01 Comparative Example 2 3.65 0.01

[0076] The above is only a preferred embodiment of the present invention, and is not any formal or substantial limitation of the present invention. It should be pointed out that ordinary technicians in this technical field can make several improvements and supplements without departing from the method of the present invention, and these improvements and supplements should also be regarded as the protection scope of the present invention. Any technician familiar with this profession, without departing from the spirit and scope of the present invention, can make some changes, modifications and evolutions of the technical content disclosed above, which are equivalent embodiments of the present invention; at the same time, any changes, modifications and evolutions of any equivalent changes made to the above embodiments based on the essential technology of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for preparing an ethylene-vinyl acetate copolymer, comprising the following steps: 1) copolymerizing ethylene and vinyl acetate at a reaction pressure of 200-400 MPa and a reaction temperature of 150-300° C. to obtain a reaction product; 2) The reaction product is depressurized and cooled to provide the desired ethylene-vinyl acetate copolymer.

2. The method for preparing ethylene-vinyl acetate copolymer according to claim 1, characterized in that: In step 1), the weight ratio of ethylene to vinyl acetate added is 5-100:0-95.

3. The method for preparing ethylene-vinyl acetate copolymer according to claim 1, characterized in that: In step 1), an initiator is further added to the copolymerization reaction, and the initiator is selected from at least one of azobisisobutyronitrile, di(2-ethylhexyl) peroxydicarbonate, tert-butyl peroxypivalate, tert-butyl peroxy-2-ethylhexanoate, tert-butyl peroxy-3,5,5-trimethylhexanoate, di-tert-butyl peroxide or benzoyl peroxide.

4. The method for preparing ethylene-vinyl acetate copolymer according to claim 3, characterized in that: The weight ratio of the initiator to the ethylene added is 0-0.009:

1.

5. The method for preparing ethylene-vinyl acetate copolymer according to claim 1, characterized in that: In step 1), the copolymerization reaction is carried out in a reactor, and the stirring speed in the reactor is 500-1000 rpm.

6. The method for preparing ethylene-vinyl acetate copolymer according to claim 1, characterized in that: In step 1), the reaction time of the copolymerization reaction is 30-120 min.

7. The method for preparing ethylene-vinyl acetate copolymer according to claim 1, characterized in that: In step 1), the reaction pressure of the copolymerization reaction is 250-350 MPa; the reaction temperature of the copolymerization reaction is 200-250°C.

8. An ethylene-vinyl acetate copolymer prepared by the method according to any one of claims 1 to 7.

9. The ethylene-vinyl acetate copolymer according to claim 8, characterized in that The ratio of the weight average molecular weight Mw to the number average molecular weight Mn of the ethylene-vinyl acetate copolymer is 1.8-12.

1.

10. Use of the ethylene-vinyl acetate copolymer according to any one of claims 8 to 9 in the fields of foaming materials, cable materials, coating materials, photovoltaic materials or film materials.

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