JPH0120989B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a multilayer structure polymer suitable for obtaining films or sheets having extremely excellent weather resistance, solvent resistance, stress whitening resistance, and excellent physical properties such as mechanical strength. Several multilayer polymers containing acrylic rubber have been proposed as materials for forming films and sheets characterized by weather resistance.
At present, it lacks stress whitening resistance, solvent resistance, etc., and has not yet been able to provide sufficiently satisfactory properties. For example, JP-A No. 52-33991,
The polymers proposed in Japanese Patent Publication No. 46158/1983 are simply multilayer polymerization of resin on a crosslinked elastic body, and do not solve the above problems. The present applicant proposed a multilayer polymer having a tapered structure as a method to solve the above-mentioned problems, and filed an application earlier (Japanese Patent Application Laid-Open No. 129449/1983;
No. 56150). This multilayer polymer is an impact-resistant polymer that has extremely excellent stress whitening resistance and transparency due to its unique tapered structure and grafting effect. By the way, new functions obtained by film-molding the above-mentioned various acrylic polymers and laminating this onto other base materials include weather resistance, stain resistance, and cosmetic properties. For example, one of the major uses is to create a cosmetic effect that cannot be obtained with the base material itself by applying various types of printing on an acrylic film and laminating them. However, general acrylic films have a major drawback in that they are not suitable for beautiful printing because they easily dissolve and swell in printing ink solvents such as toluene and methyl ethyl ketone. Furthermore, many common acrylic films do not have sufficient mechanical strength, and as a result, their uses are currently quite limited. In view of the current situation, the present inventors conducted further studies on the polymer structure in order to obtain a multilayer structure polymer that not only has excellent weather resistance and stress whitening resistance, but also excellent solvent resistance and mechanical properties. The invention has been achieved. That is, 0 to 20 parts of at least one monomer (A ₁ ) selected from 80 to 100 parts of alkyl acrylate having an alkyl group having 1 to 8 carbon atoms, aromatic vinyl, and unsaturated nitriles can be copolymerized. Monomer (A ₂ ) having a double bond: 0 to 10 parts of polyfunctional monomer (A ₃ ) 0.1 to 5 parts per 100 parts of the total amount of (A ₁ ) to (A ₃ )
The innermost layer polymer consists of a composition of graft cross-agents of
(A) 80 to 100 parts of an alkyl acrylate having an alkyl group having 1 to 8 carbon atoms (B ₁ ) 0 to 20 parts of a monomer having a copolymerizable double bond (B ₂ ) 0 to 10 parts Polyfunctional monomer (B ₃ ) 0.1 to 5 parts per 100 parts of the total amount of (B ₁ ) to (B ₃ )
51 to 100 parts of at least one monomer selected from aromatic vinyl and unsaturated nitriles (C ₁ ); 0 to 49 parts of copolymer; Consisting of a monomer (C ₂ ) with a polymerizable double bond and a glass transition temperature of at least 60°C
The outermost layer polymer (C) is the basic structural unit, and between the polymer (B) layer and the polymer (C) layer, an intermediate layer (D) containing 10 to 90 parts of an alkyl group having 1 to 8 carbon atoms is used. Alkyl acrylate (D ₁ ) having 10 to 90 parts of at least one monomer selected from aromatic vinyl and unsaturated nitriles (D ₂ ) having 0 to 20 parts of a copolymerizable double bond Monomer ( _D3 ) 0 to 10 parts polyfunctional monomer ( _D4 ) 0.1 to 5 parts per 100 parts of the total amount of ( _D1 ) to ( _D4 )
The composition has at least one intermediate layer in which the amount of alkyl acrylate in the intermediate layer (D) monotonically decreases from the crosslinked elastic polymer (B) to the outermost layer polymer (C). , and the gel content of the outer layer structure polymer is at least 50%.The multilayer structure polymer is characterized in that it has excellent weather resistance, solvent resistance, impact resistance, etc., and has excellent formability into a film.
The present invention was completed by discovering that the film is excellent in various properties required for film and sheet materials, such as tensile strength and elongation. One of the features of the present invention is that the crosslinked elastic polymer (B) has a two-layer elastic structure including the innermost layer polymer (A) as an inner layer. This solves the drawbacks of acrylic rubber, such as slow elastic recovery, large deformation under stress, and low rubber efficiency compared to diene rubber. That is, due to the presence of the innermost layer polymer (A), when stress is applied, the stress concentrated on the crosslinked elastic polymer (B) layer is polydispersively relaxed, and as a result, the incidence of microvoids is increased. It is thought that it exhibits excellent impact resistance even without apparent stress whitening. In the present invention, the alkyl acrylate having an alkyl group having 1 to 8 carbon atoms constituting the innermost layer polymer (A) may be linear or branched, and may be methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, etc. may be used alone or in combination, but those with a low Tg are more preferred. Further, as the aromatic vinyl, styrene, α-methylstyrene, halogenated styrene, etc. are used. Further, as unsaturated nitriles, acrylonitrile, methacrylonitrile, etc. are used. These alkyl acrylates, aromatic vinyl,
Unsaturated nitriles are 80 to 100 singly or in combination.
Used within the scope of the section. Furthermore, as the monomer having a copolymerizable double bond, acrylic monomers such as alkyl methacrylate, lower alkoxy acrylate, cyanoethyl acrylate, acrylamide, acrylic acid, and methacrylic acid are preferably used, and used in an amount of 0 to 20 parts. It will be done. Furthermore, as the polyfunctional monomer (A ₃ ), alkylene glycol dimethacrylates such as ethylene glycol dimethacrylate, 1,3 butylene glycol dimethacrylate, 1,4 butylene glycol dimethacrylate and propylene glycol dimethacrylate are preferred, and divinylbenzene, Polyvinylbenzenes such as trivinylbenzene and alkylene glycol diacrylates can also be used. These monomers function effectively to bridge the layer in which they are contained, and are not used for bonding between layers with other layers. Polyfunctional monomer (A ₃ )
The range of use is 0 to 10 parts. On the other hand, copolymerizable α, β
Allyl, methallyl or crotyl esters of unsaturated carboxylic or dicarboxylic acids are used, preferably allyl esters of acrylic acid, methacrylic acid, maleic acid and fumaric acid, with allyl methacrylate being especially effective. Other effective examples include triallyl cyanurate and triallyl isocyanurate. In such graft cross-agents, the conjugated unsaturated bond of the ester reacts much faster than allyl, methallyl, or crotyl groups, and
chemically bond. On the other hand, a substantial portion of the allyl group, methallyl group, and crotyl group acts effectively during the polymerization of the next layer polymer and provides a graft bond between two adjacent layers. The amount of graft cross-agent used is extremely important, and should be 0.1 to 5 parts per 100 parts of the total amount of the above components (A ₁ ) to (A ₃ ).
part, preferably in the range of 0.5 to 2 parts.
If the amount used is less than 0.1 part, the effective amount of graft bonding will be small, and if the amount used exceeds 5 parts, the amount of reaction with the crosslinked elastic polymer (B) formed by polymerization in the second stage will be large, which is a feature of the present invention. This results in a decrease in the elasticity of the two-layer crosslinked rubber elastic body having a two-layer elastic body structure. The innermost layer polymer (A) is a graft-active layer and its
Tg is appropriately set depending on the physical properties required of the final polymer. In general, it is advantageous in terms of quality that the crosslinking density is the same as or even higher than that of the crosslinked elastic polymer (B). Note that the innermost layer polymer (A) and crosslinked elastic polymer (B) may have the same composition, but it is important to create a two-layer elastic structure through two-stage polymerization rather than one-time charging. Yes, catalyst amount,
It is advantageous for the polymer (A) to have a higher crosslinking density. The content of the innermost layer polymer (A) in the multilayer structure polymer of the present invention is 5 to 35% by weight, preferably 5 to 15% by weight.
The content of the crosslinked elastic polymer (B) is preferably lower than that of the crosslinked elastic polymer (B). The crosslinked elastic polymer (B) is the main component that gives rubber elasticity to the multilayer structure polymer, and the main component is 80 to 100 parts of alkyl acrylate (B ₁ ) in which the alkyl group has 1 to 8 carbon atoms. In addition, 0 to 20 parts of other copolymerizable double bond-containing monomers (B ₂ ), polyfunctional monomers (B ₃ )
is used as appropriate in the range of 0 to 10 parts. Furthermore, 0.1 to 5 parts of a graft cross-agent is used per 100 parts of the total amount of (B ₁ ) to (B ₃ ). Among these, the components (B ₁ ) and (B ₃ ) and the grafting agent used are those exemplified for the innermost layer polymer (A). As the component (B ₂ ), in addition to the monomers exemplified for the innermost layer polymer (A), aromatic vinyl and unsaturated nitriles can be used. The Tg of the crosslinked elastic polymer (B) alone is 0°C or lower, preferably -30°C or lower to provide good physical properties. Crosslinked elastic polymer (B) in the multilayer structure polymer of the present invention
The content is preferably in the range of 10 to 45% by weight, and is preferably higher than the content of the innermost layer polymer. This two-layer crosslinked rubber elastic body in which the innermost layer polymer (A) and the crosslinked elastic polymer (B) are graft-bonded has a gel content of 85% or more and a swelling degree of 3 to 3 as determined by the following measurement method.
It is preferable to set it within the range of 13 from the viewpoint of solvent resistance and impact resistance. (Measurement method of swelling degree and gel content of cross-linked rubber elastic body) A specified amount of two-layer cross-linked rubber elastic body was sampled according to JIS K-6388, and immersed in methyl ethyl ketone (hereinafter abbreviated as MEK) at 25°C for 48 hours. After pulling it up, wipe off the adhered MEK, measure its weight, then dry and remove MEK in a vacuum dryer, measure the absolute dry weight, and calculate it using the following formula. Swelling degree = Weight after MEK swelling - Bone dry weight / Bone dry weight Gel content (%) = Bone dry weight / Weight of collected sample x 100 Generally, the higher the degree of polymerization of the crosslinked elastic polymer (B), the higher the final weight. The combined impact strength is high, which is preferable. On the other hand, this does not apply to the core innermost layer polymer (A), and in fact, it is better to use a larger amount of catalyst in order to stabilize the initial polymerization including particle formation, resulting in better performance as a two-layer crosslinked rubber elastic body. tends to be good. Furthermore, the outermost layer polymer (C) constituting the multilayer structure polymer of the present invention is for imparting moldability, mechanical properties, etc. to the multilayer structure polymer, and is composed of aromatic vinyl and unsaturated nitriles. 51 to 100 parts of at least one monomer selected from among (C ₁ ) and 0 to 49 other copolymerizable monomers having a double bond (C ₂ )
It consists of two parts. As the component (C ₂ ), those equivalent to the component (A ₂ ) and alkyl acrylates are used. The Tg of the outermost layer polymer (C) alone needs to be 60°C or higher, preferably 80°C or higher in order to obtain excellent solvent resistance. The Tg of the polymer (C) alone is
If the temperature is lower than 60° C., the solvent resistance of the final heavy material described below will not be excellent even if the gel content is 50% or more. The content of the outermost layer polymer (C) in the multilayer structure polymer of the present invention is 10 to 80% by weight, preferably 40 to 60% by weight.
It is. The multilayer structure polymer of the present invention is the innermost layer polymer described above.
(A), crosslinked elastic polymer B and outermost layer polymer (C) are the basic structural units, and 10 to 90 parts of crosslinked elastic polymer (B) layer and outermost layer polymer (C) layer are used as basic structural units. Alkyl acrylate (D ₁ ) having an alkyl group having 1 to 8 carbon atoms, 90 to 10 parts of aromatic vinyl, at least one monomer selected from unsaturated nitriles (D ₂ ), 0 to 20 parts A monomer having a copolymerizable double bond (D ₃ ), 0 to 10 parts of a polyfunctional monomer (D ₄ ), and 100 parts of the total amount of (D ₁ ) to (D ₄ )
The intermediate layer (D) is composed of a composition of 0.1 to 5 parts of graft cross-agent, and the amount of alkyl acrylate in the intermediate layer (D) decreases monotonically from the polymer (B) layer to the polymer (C) layer. At least one layer is arranged so as to Here, the components (D ₁ ) to (D ₄ ) and the grafting agent used are the same as those exemplified for the innermost layer polymer (A). The grafting agent used in the intermediate layer (D) is essential for closely bonding each polymer layer and obtaining excellent properties. The content of each intermediate layer (D) in the multilayer structure polymer of the present invention is 3 to 35% by weight, and if it is less than 5% by weight, it will not lose its function as an intermediate layer, and if it exceeds 35% by weight, it will not function as a final layer. This is not preferable because it upsets the balance of the polymer. The multilayer structure polymer of the present invention is composed of the above-mentioned polymer layers (A), (B), (C), and (D), and furthermore, the multilayer structure polymer has the desired excellent properties. In order to obtain various properties such as solvent resistance and mechanical properties, the gel content must be at least 50%, preferably at least 60%. In this case, the gel content includes the two-layer crosslinked rubber elastic body itself and the graft components of the intermediate layer (D) and outermost layer polymer (C) to the crosslinked rubber elastic body, and can be measured using the following measurement method. This is what I asked for. (Method for measuring gel content of multilayer structure polymer) Prepare a 1% by weight MEK solution of multilayer structure polymer,
After standing at 25℃ for a day and night, centrifuge at 16000r.
Centrifuge at pm for 90 minutes, dry the insoluble matter under reduced pressure to determine the absolute dry weight, and calculate the gel content using the following formula. Gel content (%) = Bone dry weight of MEK insoluble matter / Weight of collected sample x 100 In this case, the gel component is the added weight of the two-layer crosslinked rubber elastic body and the grafted chains, and it can also be replaced by the grafting rate. However, since the product of the present invention has a special structure, the gel content was used as a guideline for the amount of grafting. From the point of view of solvent resistance, the higher the gel content, the more advantageous it is, but from the point of view of easy moldability, the presence of a certain amount or more of free polymer is necessary, so the upper limit of the gel content is about 80%. preferable. When producing the multilayer structure polymer of the present invention, it is essential that the emulsion particle size of the final polymer is 0.2μ or less, and if it is 0.2μ or more, transparency and
Properties such as stress whitening resistance are significantly impaired. In particular, particles with a particle size in the range of 0.08 to 0.15 μ show the most balanced structure. The most suitable method for producing the multilayer structure polymer of the present invention is a sequential multistage polymerization method using an emulsion polymerization method, but it is not particularly limited thereto. For example, after emulsion polymerization, the outermost layer polymer (C ) can also be carried out by an emulsion suspension polymerization method in which the polymerization is converted to a suspension polymerization system during the polymerization. There are no particular restrictions on the surfactants, catalysts, etc. that may be used. Furthermore, it is possible to add a range of additives such as antioxidants, ultraviolet absorbers, and lubricants to the multilayer structure polymer of the present invention, if necessary. The present invention will be specifically described below with reference to Examples, but the present invention is not necessarily limited thereto. In addition, the abbreviations used in this example indicate the following compounds. AN: Acrylonitrile MMA: Methyl methacrylate St: Styrene BuA: Butyl acrylate AMA: Allyl methacrylate BD: 1,3 butylene glycol dimethacrylate CHP: Yumene hydroperoxide SFS: Sodium formaldehyde sulfoxylate MEK: Methyl ethyl ketone Example 1 250 parts of ion-exchanged water in a polymerization vessel with a cooler,
2 parts of ester soda salt of sulfosuccinic acid,
After adding 0.05 parts of SFS and stirring under nitrogen, 1.6 parts of St.
A mixture consisting of 8 parts BuA, 0.4 parts BD, 0.1 part AMA and 0.04 parts CHP was charged. After raising the temperature to 70°C, the reaction was continued for 60 minutes to complete polymerization of the innermost layer polymer (A). Next, St1.5 part, BuA22.5 part, BD1.0 part,
A mixture consisting of 0.25 parts of AMA and 0.0125 parts of CHP
It was added and polymerized for 60 minutes to obtain a two-layer crosslinked rubber elastic body. The swelling degree and gel content of the obtained two-layer crosslinked rubber elastic body were determined by the method described above and were 9.0 and 9.0, respectively.
It was 9.2%. Next, as the middle class (D), St6 part, AN2 part, BuA7
35 parts of St, 12 parts of AN, and finally 35 parts of St, 12 parts of AN,
A mixture consisting of 3 parts of BuA and 0.025 parts of CHP was added over 120 minutes and maintained at that temperature for 60 minutes to form an outermost layer polymer (C), and a multilayer structure polymer (invention product 1 ) was obtained. Inventive products 2 and 3 having the compositions shown in Table 1 were polymerized in exactly the same manner. Further, as comparative examples, a product having a single rubber structure (Comparative Example 1) and a product having the same composition as Invention Product 1 and having a particle size of 0.2 μ or more (Comparative Example 2) were also polymerized in the same manner. The particle size of each of the obtained multilayer structure polymers was 0.11 to 0.12μ in all cases except for Comparative Example 2. These obtained polymer emulsions were salted out using 5 parts of calcium chloride per 100 parts of the polymer.
After washing, dehydration, and drying, a stabilizer was added and shaped, and various evaluations were performed. The gel content of each of these multilayer polymers was 60% or more, except for Comparative Example 1. Furthermore, each of these multilayer structure polymers could be easily formed into a 50μ film by a conventional method. As is clear from the results in Table 1, all the products of the present invention exhibit excellent solvent resistance and resistance to whitening upon bending.
Comparative Example 2, which has a particle size of 0.2 μm or more, has poor whitening resistance when folded, although it exhibits sufficient film strength.
Comparative Example 1, in which the rubber structure does not have a two-layer structure and no graft cross-agent is used in the (D) layer.
Both physical properties are poor. Also, products 1 to 3 of the present invention
As for
Despite accelerated exposure for 3000 hours, no change in appearance was observed in either case.

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Claims (1)

[Scope of Claims] 1 80 to 100 parts by weight (hereinafter abbreviated as parts) of at least one unit selected from alkyl acrylates having an alkyl group having 1 to 8 carbon atoms, aromatic vinyls, and unsaturated nitriles. Monomer (A ₁ ) 0 to 20 parts of a monomer having a copolymerizable double bond (A ₂ ) 0 to 10 parts of a polyfunctional monomer (A ₃ ) (A ₁ ) to (A ₃ ) 0.1 to 5 per 100 copies
The innermost layer polymer consists of a composition of graft cross-agents of
(A) 80 to 100 parts of an alkyl acrylate having an alkyl group having 1 to 8 carbon atoms (B ₁ ) 0 to 20 parts of a monomer having a copolymerizable double bond (B ₂ ) 0 to 10 parts Polyfunctional monomer (B ₃ ) 0.1 to 5 parts per 100 parts of the total amount of (B ₁ ) to (B ₃ )
51 to 100 parts of at least one monomer selected from aromatic vinyl and unsaturated nitriles (C ₁ ); 0 to 49 parts of copolymer; Consisting of a monomer (C ₂ ) with a polymerizable double bond and a glass transition temperature of at least 60°C
The outermost layer polymer (C) is the basic structural unit, and the intermediate layer (D) is between the polymer (B) layer and the polymer (C) layer. Acrylate (D ₁ ) 90 to 10 parts of at least one monomer selected from aromatic vinyl and unsaturated nitriles (D ₂ ) 0 to 20 parts of a monomer having a copolymerizable double bond ( _D3 ) 0 to 10 parts of polyfunctional monomer ( _D4 ) 0.1 to 5 parts per 100 parts of the total amount of ( _D1 ) to ( _D4 )
The composition has at least one intermediate layer in which the amount of alkyl acrylate in the intermediate layer (D) monotonically decreases from the crosslinked elastic polymer (B) to the outermost layer polymer (C). , and the gel content of the multilayered structure is at least 50%, and the emulsion particle size of the final polymer during emulsion polymerization is 0.2μ or less, weather resistance, stress whitening resistance, solvent resistance, and mechanical properties. A multilayer polymer with excellent physical properties.