JPH0535173B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an impact modifier that can impart high impact resistance and good moldability. Thermoplastic resins, particularly vinyl chloride resins (hereinafter abbreviated as PVC), are widely used as general-purpose resins, but their mechanical properties are not always satisfactory. That is, PVC has poor impact strength, particularly notched impact strength, and various methods have been proposed to improve this impact strength. The most effective method among these proposals is to mix PVC with a multilayer graft copolymer obtained by graft polymerizing monomers of styrene, methyl methacrylate, and acrylonitrile acid onto a conjugated diene elastomer. Such multilayer graft copolymers have already been developed.
It is commercially available as an impact modifier for PVC.
This has greatly contributed to expanding the applications of PVC molded products. By the way, in profile extrusion applications, there is a demand for compositions that have very strong slipperiness and have high impact strength even when molded under conditions where kneading is not effective. Modifiers do not provide sufficient results. In other words, multilayer graft copolymers, which are conventional impact modifiers in which a resin component with good compatibility with PVC is graft-polymerized onto an elastomer, do not work well when processed at high temperatures or when a relatively small amount of lubricant is used. While multilayer graft copolymers are uniformly dispersed in PVC and exhibit good impact resistance, multilayer graft copolymers are
It aggregates in PVC and exhibits almost no impact resistance. The present inventors have developed such a multilayer graft copolymer.
As a result of intensive studies based on the idea that uniform dispersion in PVC is the most effective way to improve impact resistance, we found that the glass transition temperature (hereinafter abbreviated as Tg) of the outermost layer is higher than that of conventionally known multilayer graft copolymers. When a multilayer graft copolymer with a temperature of 0°C or less is blended with PVC and molded, it not only has a good dispersion state even under molding conditions with high kneading, but also has low kneading and low shear stress. Even at low temperatures, the multilayer graft copolymer melts quickly, gels quickly, and has an extremely good dispersion state, exhibits high impact strength under a wide range of molding conditions, and has good processability and a molded product with excellent surface gloss. The inventors have discovered that this can be done, and have arrived at the present invention. That is, the gist of the present invention is that the crosslinking agent is 0.
At least two graft layers on a butadiene-based elastomer (A) consisting of polybutadiene containing ~5% by weight or a copolymer of 50% by weight or more of butadiene and 50% by weight or less of another vinyl compound that can be copolymerized with it. is an impact resistance modifier made of a multilayer graft copolymer obtained by graft polymerization, and the graft layer is a monomer made of an acrylic acid alkyl ester, a methacrylic acid alkyl ester, an aromatic vinyl compound, a vinyl cyanide compound, and butadiene. Each graft layer contains a crosslinking agent in an amount of 0 to 5% by weight relative to each layer, and the Tg of the polymer constituting the outermost layer (C) is 0°C or less.
The Tg of the polymer constituting the second layer (B) from (C) is 60
It is an impact modifier that is above ℃. It is essential that the impact resistance modifier of the present invention has a multilayer structure of three or more layers obtained by polymerization in at least three stages, and of course, even if there are three or four graft layers. There is no problem, as long as the polymer structure satisfies that the Tg of the polymer in the outermost layer is 0°C or less, and the Tg of the polymer in the second layer counting from the outermost layer is 60°C or more.
As long as the Tg is within the range, other monomers or monomer mixtures may of course be polymerized in multiple stages depending on the purpose. The monomer group constituting the impact modifier of the present invention is composed of an acrylic acid alkyl ester, a methacrylic acid alkyl ester, an aromatic vinyl compound, a vinyl cyanide compound, and butadiene. The acrylic acid alkyl ester preferably has an alkyl group having 2 to 10 carbon atoms, such as ethyl acrylate, propyl acrylate, n-butyl acrylate, isobutyl acrylate, hexyl acrylate, octyl acrylate, and acrylic acid. Examples include 2-ethyl-hexyl acid. The methacrylic acid alkyl ester preferably has an alkyl group having 1 to 4 carbon atoms, such as methyl methacrylate, ethyl methacrylate,
Examples thereof include propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, and tertiary butyl methacrylate. Considering compatibility with PVC, methyl methacrylate is particularly preferred. In addition, aromatic vinyl compounds include styrene,
Examples include α-substituted styrene, nuclear-substituted styrene, and derivatives thereof, such as α-methylstyrene, chlorostyrene, vinyltoluene, and the like. Furthermore, examples of vinyl cyanide compounds include acrylonitrile and methacrylonitrile. Furthermore, examples of butadiene include 1,2-butadiene and 1,3-butadiene. The outermost layer (C) component constituting the impact modifier of the present invention is selected from the above monomer group so that the outermost layer (C) itself has a Tg of 0° C. or less. The composition ratio of the monomers in the outermost layer (C) is 0 to 100% by weight of alkyl acrylate, 0 to 40% by weight of alkyl methacrylate, and 0 to 40% by weight of aromatic vinyl compound.
It can be used in a range of 0 to 20% by weight of vinyl cyanide compound and 0 to 100% by weight of butadiene.
If the Tg of the outermost layer (C) itself exceeds 0°C, it is difficult to obtain the desired impact resistance improvement effect sufficiently. Furthermore, acrylic acid alkyl ester is preferable to butadiene in that it can be polymerized under normal pressure. The proportion of the outermost layer (C) in the total amount of the multilayer graft copolymer is preferably 10 to 60% by weight. If the proportion is less than 10% by weight, the effect of improving impact resistance will be small, and if the proportion exceeds 60% by weight, it will be PVC. This is not preferable since it deteriorates the molding processability when blending and molding. Furthermore, the components of the second layer (B) counted from the outermost layer (C) are selected from the above monomer group so that the Tg of the layer (B) itself is 60° C. or higher. The composition ratio of the monomers in the layer (B) is 0 to 100% of the alkyl methacrylate ester.
100% by weight, aromatic vinyl compound 0-100% by weight,
The vinyl cyanide compound can be used in a range of 0 to 30% by weight, and the acrylic acid alkyl ester can be used in a range of 0 to 20% by weight. If the Tg of the layer (B) itself is less than 60°C, the multilayer graft copolymer particles tend to aggregate, resulting in poor impact resistance. As a component of layer (B), when blended with PVC, methacrylic acid alkyl ester is preferred, and methyl methacrylate is particularly preferred. Aromatic vinyl compounds improve the fluidity of PVC during blend molding, but when used in large amounts, compatibility deteriorates and impact resistance decreases. Furthermore, a vinyl cyanide compound is preferable because it promotes gelation when blended with PVC, but if a large amount is used, discoloration tends to occur during molding and processability deteriorates. The proportion of the layer (B) in the total amount of the multilayer graft copolymer is preferably 20 to 60% by weight, and a proportion of less than 20% by weight is not preferable because molding processability when blended with PVC and molded is poor. Further, if the proportion exceeds 60% by weight, the amount of the elastic component in the entire multilayer graft copolymer decreases, which is not preferable because the effect of improving impact resistance is small. The diene-based elastomer (A) contains a rubber component that serves as the base of the multilayer graft copolymer, and this rubber component is composed of polybutadiene or a copolymer of 50% by weight or more of butadiene and 50% by weight or less of another vinyl compound that can be copolymerized therewith. It is a polymer. Other vinyl compounds that can be copolymerized include styrene, acrylonitrile, and the like. The proportion of the diene elastomer (A) in the total amount of the multilayer graft copolymer is preferably 10 to 60% by weight, and if the proportion is less than 10% by weight, the effect of improving impact resistance will be small.
Further, if the proportion exceeds 60% by weight, not only will it be difficult to coagulate the emulsion polymer latex, but also the moldability will be poor when blended with PVC and molded. The polyfunctional crosslinking agent of the present invention not only facilitates graft cross-linking when producing the impact modifier of the present invention, but also significantly improves the coagulation properties of the emulsion polymer latex. . Examples of the polyfunctional crosslinking agent include divinylbenzene, diacrylic ester or dimethacrylic ester which is an ester of acrylic acid or methacrylic acid and polyhydric alcohol, or triallyl cyanurate, triallyl isocyanurate, allyl acrylate, and allyl methacrylate. , diallyl itaconate,
Examples include diallyl phthalate. Note that in consideration of graft cross-reactivity, a crosslinking agent having an allyl group is preferable. The proportion of the polyfunctional crosslinking agent in each layer is 0 to 5% by weight. If the amount exceeds 5% by weight, the elastic properties of the diene elastic layer (A) or layer (C) will be severely impaired. Also, the resin layer (B) is
Both are unfavorable because their compatibility with PVC deteriorates and the effect of improving impact resistance decreases. The proportion of the multifunctional crosslinking agent in each layer is 0.1 to 3% by weight, considering the coagulation properties of the emulsion polymer latex during production of the multilayer graft copolymer and the effect of improving the impact resistance of the resulting multilayer graft copolymer. A range of % is preferred. The multilayer graft copolymer that is the impact modifier of the present invention is preferably produced by a conventional emulsion polymerization method. Examples of emulsifiers include anionic surfactants such as fatty acid salts, alkyl sulfate ester salts, alkylbenzene sulfonates, alkyl phosphate ester salts, and dialkyl sulfosuccinates, as well as polyoxyethylene alkyl ethers and polyoxyethylene fatty acid esters. , sorbitan fatty acid ester,
Nonionic surfactants such as glycerin fatty acid esters and cationic surfactants such as alkylamine salts can be used. These surfactants can be used alone or in combination. Furthermore, when the pH of the polymerization system is on the acrylic side depending on the type of emulsifier, an appropriate pH regulator may be used to prevent hydrolysis of the acrylic acid alkyl ester. As a polymerization initiator, an inorganic initiator such as a normal persulfate, an organic peroxide, an azo compound, etc. may be used alone, or the above compound and a sulfite, hydrogen sulfite, thiosulfate, primary A combination of metal salts, sodium formaldehyde sulfoxylate, etc. can also be used as a redox initiator. Preferred persulfates as initiators include sodium persulfate, potassium persulfate, ammonium persulfate, etc., and organic peroxides include t-butyl hydroperoxide, cumene hydroperoxide, benzoyl peroxide, lauroyl peroxide, etc. be. A chain transfer agent may be used to adjust the molecular weight of the polymer, and alkyl mercaptans having 5 to 20 carbon atoms can be used. Polymerization is carried out at a temperature higher than the decomposition temperature of the initiator under normal emulsion polymerization conditions, at least the outermost layer (C) and the outermost layer.
This can be done so that the second layer (B) from (C) and the diene elastic body (A) have the structure described above. At this time, the polymerization at each stage can be carried out by adding the entire amount of each monomer or monomer mixture at once, or while continuously adding the entire amount or part of the monomer or monomer mixture. However, from the viewpoint of stability of polymerization, removal of heat of polymerization reaction, etc., it is preferable to carry out polymerization while adding all or part of it. The particle size of the multilayer graft copolymer has a large effect on the impact strength of the PVC resin composition. If the particle size is too small, the effect of improving impact strength will be small, and it is preferable to make it as large as possible without impairing the stability of the latex. The particle size of the graft copolymer is
The range of 0.15 to 0.40μ is good, and the appropriate emulsifier type/
It can also be adjusted by volume or by using thickening agents such as acids or inorganic salts in appropriate polymerization steps. When recovering the multilayer graft copolymer from the obtained latex, salting out or acid precipitation is performed,
It can be recovered in powder form after filtration and washing with water, or it can be recovered by spray drying, freeze drying, etc. Furthermore, it can also be recovered by the method disclosed in JP-A-57-187322. The impact modifier of the present invention is a graft copolymer having a multilayer structure as described above, which imparts high impact resistance and good processability to various thermoplastic resins, and improves the appearance of molded products. It shall be in good condition. The proportion of the impact modifier of the present invention mixed with the thermoplastic resin is 3 to 3 parts by weight per 100 parts by weight of the thermoplastic resin.
50 parts by weight. If the blending ratio is less than 3 parts by weight, the effect of improving impact resistance will be small, and if the blending ratio exceeds 50 parts by weight, the mechanical properties inherent to the thermoplastic resin will be impaired, so both are not preferred. Here, thermoplastic resins include PVC, polycarbonate resin,
Examples include polyester resin, acrylonitrile-styrene resin, methyl methacrylate-styrene resin, and the like. As PVC, in addition to polyvinyl chloride, a vinyl chloride copolymer containing 70% by weight or more of vinyl chloride can be used. As the monomer to be copolymerized with vinyl chloride, ethylene, propylene, vinyl bromide, vinylidene chloride, vinyl acetate, acrylic ester, methacrylic ester, etc. are used. The impact modifier of the present invention and the thermoplastic resin are preferably blended in powder form using, for example, a ribbon blender, a Henschel mixer, etc., and are blended using a known kneading machine, such as a mixing roll, a Banbury mixer, an extruder, or an injection molding machine. It is molded using a molding machine or the like. In addition, when compounding, known stabilizers, plasticizers, lubricants, colorants, etc. may be added as necessary. The present invention will be specifically explained below using Examples.
In the Examples and Comparative Examples, "parts" and "%" mean "parts by weight" and "% by weight," respectively. In addition, the Tg of the copolymer in each example and comparative example
is calculated from Fox's formula. Example 1 (a) Production of rubber elastic body (A) A rubber elastic body (A) was synthesized according to the following composition. 1,3-Butadiene 75 parts Styrene 25 parts Diisopropylbenzene hydroperoxide
0.2〃 Sodium pyrophosphate 0.5〃 Ferrous sulfate 0.01〃 Dextrose 1.0〃 Potassium oleate 0.5〃 Water 200〃 A mixture of the above composition was heated at 50℃ in a pressure autoclave.
Polymerization was carried out using Polymerization was completed in 15 hours. The average particle diameter of the obtained rubber was 0.16μ. (b) Production of multilayer graft copolymer Add 30 parts of the rubber latex obtained in (a) above (as a solid component of the polymer) to semi-hardened beef tallow potassium soap.
A solution of 0.6 parts of sodium formaldehyde sulfoxylate and 0.2 parts of sodium formaldehyde sulfoxylate dissolved in 120 parts of water was added, and the temperature was raised to 70°C while stirring. The temperature of this latex was maintained at 70℃ and methyl methacrylate was heated to 39.8℃.
A mixture consisting of 1.5 parts of triallylisocyanurate, 0.2 parts of triallylisocyanurate, and 0.15 parts of cumene hydroperoxide was added dropwise over a period of 2 hours and 30 minutes, and after the completion of the addition, the mixture was maintained for 1 hour to complete the first stage graft polymerization. The polymerization rate was 99.8%. To the obtained polymer latex were added 0.3 parts of semi-hardened beef tallow potash soap, 0.2 parts of sodium formaldehyde sulfoxylate dissolved in 20 parts of water, 29.8 parts of n-butyl acrylate, 0.2 parts of triallyl isocyanate, A mixture consisting of 0.15 parts of cumene hydroperoxide was added dropwise over a period of 2 hours while maintaining the temperature at 70°C, and after the completion of the addition, the mixture was maintained for 1 hour to complete the polymerization. The polymerization rate is 99.6%,
The particle size of the final graft copolymer was 0.21μ. To this graft copolymer latex, 1.0 part of 2,6-di-tert-butyl-P-cresol was added as a stabilizer.
Add 0.5 part of dilauryl thiodipropionate,
It was coagulated with a 1% aqueous sulfuric acid solution, washed, dehydrated, and dried to obtain a white powdered resin (Example 1-1)). Furthermore, a multilayer graft copolymer was obtained using the same polymerization recipe as described above while varying the proportions of each component (A), (B), and (C). These are shown in Table 1. (c) Production of blended composition with vinyl chloride resin 10 parts of the graft copolymer obtained in the above (b) and 90 parts of vinyl chloride resin with an average degree of polymerization of 700, for a total of 100 parts, and 20 parts of tribasic sulfate. , dibasic stearic acid 0.3
1 part, 2.0 parts of lead stearate, and 0.3 parts of stearic acid were added, and the temperature was raised to 115° C. in a Henschel mixer to obtain a homogeneous mixture. This vinyl chloride composition was formed into a square bar using a 30 mmφ single screw extruder under the following conditions.

[Table] This formulation and molding conditions require very little kneading. The impact strength of the molded product is ASTM D.
-256, the U-notched Izot impact test was conducted. These measurement results are also shown in Table 1. Comparative Example 1 Semi-cured beef tallow potassium soap was added to 60 parts of the rubber latex produced in (a) of Example 1 (as polymer solid content).
A solution of 0.6 parts of sodium formaldehyde sulfoxylate and 0.2 parts of sodium formaldehyde sulfoxylate dissolved in 70 parts of water was added, and the temperature was raised to 70°C while stirring. The temperature of this latex was maintained at 70℃ and methyl methacrylate was heated to 39.8℃.
A mixture consisting of 1 part, triallyl isocyanurate, 0.2 parts, and cumene hydroperoxide was added dropwise over 2 hours and 30 minutes, and after the addition was completed, the mixture was maintained for 1 hour to complete the graft polymerization. Polymerization rate is 99.8
%, and the particle size of the final graft copolymer is
It was 0.20μ. The graft copolymer was recovered from this polymer latex in the same manner as in Example 1. A composition prepared by blending this graft copolymer according to the same formulation as in Example 1 (c) was molded into a square bar under the same conditions and subjected to the same U-notched Izo impact test. The results are also shown in Table 1. Comparative Example 2 Semi-cured beef tallow potash soap was added to 30 parts of the rubber latex produced in (a) of Example 1 (as polymer solid content).
A mixture of 29.8 parts of n-butyl acrylate, 0.2 parts of triallylisocyanurate, and 0.15 parts of cumene hydroxide was heated to 70°C. The solution was added dropwise over 2 hours while maintaining the temperature. After the dropwise addition was completed, the mixture was maintained for 1 hour to complete the polymerization. The polymerization rate was 99.5%. To this polymer latex, 0.6 parts of semi-hardened beef tallow potassium soap and 0.2 parts of sodium formaldehyde sulfoxylate dissolved in 10 parts of water were added.
Methyl methacrylate 39.8 parts, triallyl isocyanurate 0.2 parts, cumene hydroperoxide 0.15 parts
dropwise over 2 hours and 30 minutes,
After the dropwise addition was completed, the mixture was maintained for 1 hour to complete the polymerization. The polymerization rate was 99.8%, and the average particle diameter of the resulting graft copolymer was 0.21μ. The graft copolymer was recovered from this polymer latex in the same manner as in Example 1. A composition containing this graft copolymer according to the same formulation as in Example 1 (c) was molded into a square bar under the same conditions and subjected to the same notched Izot impact test. The results are also shown in Table 1.

[Table] The abbreviations in Table 1 are as follows, and the same applies to the following cases. Ba: 1,3-butadiene St: Styrene MMA: Methyl methacrylate BA: n-butyl acrylate TAIC: Triallylisocyanate Bd and St of the diene elastomer (A) component in Table 1
The ratio of all is Bd/St=75/25 (parts). From the above results, it can be seen that the present invention has a dramatically greater impact strength improvement effect than Comparative Examples 1 and 2. Example 2 A mixture consisting of 27.9 parts of styrene and 0.1 part of allyl methacrylate and a mixture of 11.9 parts of methyl methacrylate and 0.1 part of allyl methacrylate as the component (B) were prepared in the proportions shown in Table 2 as the (A) component. Same as (a) and (b) of Example 1 except that the polymerization was carried out in two stages and a mixture consisting of 29.8 parts of 2-ethylhexyl acrylate and 0.2 parts of allyl methacrylate was further polymerized as component (C). Polymerization operation was carried out. Table 2 shows the impact resistance of a vinyl chloride composition obtained by operating the thus obtained graft copolymer in the same manner as in Example 1 (c). This resin composition has a graft copolymer with the same refractive index as PVC, so
Shows good transparency. In addition, the impact resistance improvement effect of similarly changing the (A) component, (B) component, and (C) component is shown in Table 2 as Examples 2-2), 2.3) and Comparative Examples 3 and 4.
It is also shown in .

[Table] The abbreviations in Table 2 are as follows. Component (B) was polymerized in two stages. AMA: Allyl methacrylate 2EHA: 2-ethylhexyl acrylate In Table 2, Examples 2-1) and 2-2)
and Bd of the diene-based elastomer (A) component of Comparative Example 4.
The ratio of St is Bd/St=75/25 (parts), and the ratio of Bd and St in the diene elastic material (A) component of Example 2-3) is Bd/St=60/40 (parts). ), and that of Comparative Example 3 is Bd/St=30/70 (parts). From the above results, it can be seen that component (A) or component (C) with a high Tg has little impact resistance improvement effect. Example 3 A butadiene-styrene copolymer (A) was synthesized using the same recipe as in Example 1 (a). Graft polymerization was performed on 30 parts of the obtained rubber latex (in terms of polymer solid content) in the same manner as in Example 1 (b). However, as component (B), a mixture consisting of 34.8 parts of methyl methacrylate, 5 parts of acrylonitrile, and 0.2 parts of triallylisocyanurate was polymerized. Furthermore, as component (C), a mixture consisting of 29.8 parts of n-octyl acrylate and 0.2 parts of triallyl isocyanurate was polymerized. Table 3 shows the effect of improving the impact resistance of the vinyl chloride composition obtained by operating the obtained graft copolymer in the same manner as in Example 1 (c). Table 3 also shows the effect of improving the impact resistance of graft copolymers in which the amounts of crosslinking agents in component (B) and component (C) were changed in the same manner as Example 3-2) and Comparative Example 5.

[Table] The abbreviations in Table 3 are as follows. OA: n-octyl acrylate AN: acrylonitrile Bd and St of the diene elastomer (A) component in Table 3
The ratio of all is Bd/St=75/25 (parts). From the above results, it can be seen that when large amounts of the crosslinking agents of components (B) and (C) are used, the effect of improving impact resistance is small.

Claims (1)

[Scope of Claims] 1. A butadiene-based elastic material containing 0 to 5% by weight of a crosslinking agent, consisting of polybutadiene or a copolymer of 50% by weight or more of butadiene and 50% by weight or less of another vinyl compound that can be copolymerized with it. It is an impact resistance modifier made of a multilayer graft copolymer in which at least two graft layers are graft-polymerized on the body (A), and the graft layer is composed of an acrylic acid alkyl ester, an acrylic acid alkyl ester,
Consisting of monomers selected from the monomer group consisting of methacrylic acid alkyl ester, aromatic vinyl compound, vinyl cyanide compound, and butadiene,
Each graft layer contains 0 to 5% by weight of a crosslinking agent with respect to each layer, the glass transition temperature of the polymer constituting the outermost layer (C) is 0°C or less, and the second layer (B) from the outermost layer (C) ) The impact resistance modifier is characterized in that the glass transition temperature of the polymer constituting it is 60°C or higher. 2 The proportion of the butadiene-based elastomer (A) in the multilayer graft copolymer is 10 to 60% by weight, and the outermost layer (C) is the glass transition of the polymer that constitutes the layer (C) from the monomer group. A polymer consisting of 95 to 100% by weight of at least one monomer selected such that the temperature is 0°C or less and 0 to 5% by weight of a crosslinking agent, and the proportion in the multilayer graft copolymer is 10% by weight. ~60% by weight, the second layer (B) from the outermost layer (C) is selected from the monomer group so that the glass transition temperature of the polymer constituting layer (B) is 60°C or higher. A polymer consisting of 95 to 100% by weight of at least one monomer and 0 to 5% by weight of a crosslinking agent,
And the proportion in the multilayer graft copolymer is 20~
60% by weight of the impact modifier according to claim 1.