JPH0361697B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a vinyl chloride resin composition that has excellent weather resistance, impact resistance, and moldability. Although vinyl chloride resins are widely used as general-purpose resins, their mechanical properties are not always satisfactory. Since vinyl chloride resin (hereinafter abbreviated as PVC) has poor impact strength (particularly notched impact strength), various modifiers have been proposed for the purpose of improving impact strength. The most effective method is to blend MBS resin, which is a conjugated diene elastomer with a methacrylic acid ester and an aromatic vinyl, or an ABS resin, which is a vinyl cyanide compound and an aromatic vinyl, with PVC. ing. However, since these copolymers contain many double bonds in the main chain of the elastomer component, if they are used outdoors for a long time, they tend to cause a yoking phenomenon and a decrease in impact strength, so they are not suitable for outdoor use. do not have. In order to compensate for these drawbacks, we used saturated polyacrylic acid alkyl ester as the rubber-like elastic material,
Methacrylic acid alkyl ester, aromatic vinyl,
Various compositions with good weather resistance have also been proposed in which a copolymer obtained by graft polymerization of a vinyl cyanide compound or the like is blended with PVC. However, these copolymers do exhibit MBS under conditions of good kneading (hereinafter referred to as low slip conditions).
Alternatively, the impact strength is equivalent to that of a composition blended with ABS resin, but under conditions where kneading is difficult, such as when a large amount of lubricant is used or when processing is performed at a relatively low temperature (hereinafter referred to as high-lubricity conditions). shows almost no impact strength improvement effect. A method using an elastic material in which saturated acrylic acid alkyl ester is partially replaced with a conjugated diene has also been proposed, and it is said that it is possible to obtain a composition that has impact strength equivalent to MBS or ABS resin even under highly slippery conditions. However, although it is not as bad as MBS and ABS resins, it still has the disadvantage of poor weather resistance. The present inventors found that when molded under highly slippery conditions,
We conducted a thorough investigation into why graft copolymers using acrylic acid alkyl ester elastomers have inferior impact strength compared to MBS or ABS resins.
As a result, when adding a crosslinking agent to an acrylic acid alkyl ester elastomer and performing graft polymerization, (1) a large amount of crosslinking agent is required to obtain sufficient graft cross-linking, which impairs rubber elasticity;
Inability to obtain sufficient impact strength (2) Sufficient graft cross-linking cannot be obtained with the amount of crosslinking agent within the range that provides appropriate rubber elasticity, and therefore compatibility with PVC becomes poor under high lubricity conditions. ,
It was confirmed that the dispersion state deteriorated and high impact strength could not be obtained. In order to overcome such problems, the present inventors have made intensive studies and found that (i) 99.9 to 99.2% by weight of an acrylic acid alkyl ester having 2 to 10 carbon atoms in the alkyl group;
30-70% mixture of 0.1-0.8% by weight of cross-linking agent and
Part by weight is subjected to emulsion polymerization to form a polymer having rubber elasticity (first step), (ii) in the presence of this emulsion polymer, 2 is added to the alkyl group.
70 to 30 parts by weight of a mixture consisting of 99 to 97% by weight of an acrylic acid alkyl ester having ~10 carbon atoms and 1 to 3% by weight of a polyfunctional grafting agent having one or more allyl groups (provided that (i ) and (ii) (with the total amount of components being 100 parts by weight) are polymerized to form an acrylic elastic body (A) having a two-layer structure with different crosslinking densities (second step), and (iii) this A monomer or monomer mixture consisting of 100 parts by weight of acrylic elastomer (A), 100 to 60% by weight of an alkyl methacrylate, 40 to 0% by weight of an aromatic vinyl compound, and 20 to 0% by weight of a vinyl cyanide compound. Graft copolymer (B) 3-30 obtained by graft polymerizing 25-125 parts by weight in one or multiple stages
Parts by weight of vinyl chloride polymer or vinyl chloride copolymer containing 70% by weight or more of vinyl chloride97~
It has been found that by blending 70 parts by weight (total amount 100 parts by weight), a composition exhibiting sufficiently high impact strength even under highly slippery conditions can be obtained. That is, in the first step, a polymer having sufficient rubber elasticity is formed using an acrylic acid alkyl ester and a small amount of a crosslinking agent, and in the second step, a mixture consisting of a large amount of a polyfunctional graft cross-linking agent and an acrylic acid alkyl ester is formed. By polymerizing, it becomes possible to maintain sufficient rubber elasticity and achieve sufficient graft cross-linking during subsequent graft polymerization.
This is a copolymer grafted onto an acrylic elastomer with a two-layer structure with different crosslink densities.
The composition blended with PVC shows good dispersion of the graft copolymer in PVC over a wide range of molding conditions from low lubricity conditions to high lubricity conditions.
The present invention was achieved by discovering that it exhibits high impact strength. The acrylic acid alkyl esters used in the first and second stages include those having 2 to 10 carbon atoms in the alkyl group, such as ethyl acrylate, propyl acrylate, n-butyl acrylate, isobutyl acrylate, Hexyl acrylate, n-octyl acrylate, 2-ethylhexyl acrylate, and the like are used. These monomers may be used alone or in combination, and of course different monomers may be used in the first stage and the second stage. The crosslinking agent used in the first step is divinylbenzene, diacrylic ester or dimethacrylic ester, which is an ester of acrylic acid or methacrylic acid and a polyhydric alcohol. In addition, as this crosslinking agent, 1
It is also possible to use graft-crosslinking polyfunctional crosslinking agents having more than one allyl group, such as triallyl cyanurate, triallyl isocyanurate, allyl methacrylate, allyl acrylate, diallyl itaconate and diallyl phthalate. This first stage crosslinking agent is used in an amount ranging from 0.1 to 0.8% by weight based on the mixture with the acrylic acid alkyl ester. By using a relatively small amount of crosslinking agent in this manner, a polymer having a low crosslinking density and exhibiting good rubber-like elasticity can be obtained. The graft crosslinking agent used in the second step is a graft crosslinking polyfunctional crosslinking agent having one or more allyl groups in its molecule, which has a crosslinking effect and forms a graft initiation point during graft polymerization. For example, triallyl cyanurate, triallyl isocyanurate, allyl methacrylate, allyl acrylate, diallyl itaconate, diallyl phthalate, etc. can be used. If the graft cross-agent used in the second step does not have an allyl group, sufficient graft cross-reaction cannot be expected. The amount of grafting agent used is 1 to 3% by weight, based on the mixture with the acrylic acid alkyl ester. If it is less than 1% by weight, sufficient graft cross-linking cannot be obtained and sufficient impact resistance cannot be imparted under high-lubricity molding conditions. If it exceeds 3% by weight, the elasticity of the elastic body in the second stage portion will be too impaired and impact resistance will be lost. In producing the acrylic elastomer (A), ordinary anionic, cationic, or nonionic surfactants can be used as emulsifiers. Furthermore, when the pH of the polymerization system becomes alkaline depending on the type of emulsifier used, an appropriate pH regulator may be used to prevent hydrolysis of the acrylic acid alkyl ester. As a PH regulator, boric acid
Potassium chloride - sodium hydroxide, potassium dihydrogen phosphate - disodium hydrogen phosphate, boric acid - potassium chloride - sodium carbonate, boric acid - sodium carbonate, potassium hydrogen citrate - citric acid, potassium dihydrogen phosphate - borax , disodium hydrogen phosphate-citric acid, etc. can be used. As the polymerization initiator, ordinary water-soluble inorganic initiators such as persulfates can be used alone, or they can be used in combination with sulfites, bisulfites, thiosulfates, etc. as redox initiators. Furthermore, redox initiators such as organic hydroperoxide-ferrous salts, organic hydroperoxide-sodium formaldehyde sulfoxylate, or azo compounds can also be used. Polymerization can be carried out at a temperature above the decomposition temperature of the initiator and under conventional emulsion polymerization conditions. Both the first and second stage polymerizations can be carried out by adding the entire amount of each monomer mixture at once, or while continuously adding the entire amount or a portion thereof. 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 elastic latex has a large effect on the impact strength of the PVC resin composition. This is PVC
This is because the size of the dispersed particles of the modifier dispersed in the polymer is controlled; if it is too small, it is unfavorable for impact strength, and it is preferable that it is as large as possible without impairing the stability of the latex. .
The particle size of the elastic latex is preferably in the range of 0.15 to 0.35μ, and when using rubber with a relatively small particle size, it is necessary to use an appropriate enlarging agent such as an acid or an inorganic salt before or during graft polymerization. It is also possible to adjust the particle size. The graft copolymer (B) was prepared in the presence of 100 parts by weight (as solid content) of the acrylic elastomer (A) latex.
Obtained by graft polymerization of ~125 parts by weight of monomer or monomer mixture. If the amount of the monomer or monomer mixture to be graft-polymerized exceeds 125 parts by weight, the effect of improving impact properties will be small when blended with PVC resin. If the amount of the monomer or monomer mixture to be graft-polymerized is less than 25 parts by weight, not only will it be difficult to operate the graft copolymer during the coagulation and drying process, but the moldability of the PVC resin composition will be extremely poor. The impact strength is also low. As monomers to be grafted, methacrylic acid alkyl esters, aromatic vinyls, vinyl cyan compounds, etc. can be used, and each can be graft-polymerized in one stage or in multiple stages, either alone or in combination. Methacrylic acid alkyl ester has an alkyl group having 1 to 4 carbon atoms, methyl methacrylate,
Ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, iso-butyl methacrylate, tert-butyl methacrylate, etc. can be used, but considering compatibility with PVC, methyl methacrylate is preferred. is preferred. As the aromatic vinyl compound, in addition to styrene, α-substituted styrene, nuclear-substituted styrene, and derivatives thereof, such as vinyltoluene, α-methylstyrene, chlorostyrene, etc. are used. As the vinyl cyanide compound, acrylonitrile, methacrylonitrile, etc. are used. The amount of the methacrylic acid alkyl ester used can be 100 to 60% by weight based on the total amount of the graft portion. If the amount used is less than 60%, the dispersion state of the graft copolymer in the PVC resin under high-lubricity molding conditions will deteriorate, resulting in a decrease in impact resistance and a deterioration in surface gloss. An aromatic vinyl compound can also be used to improve fluidity, but the amount used is 0 to 40% by weight based on the total amount of the grafted portion. If the amount used exceeds 40% by weight, the compatibility with the PVC resin will deteriorate and the impact resistance will decrease. The vinyl cyanide compound can be used in an amount of 20 to 0% by weight based on the total amount of the graft portion. vinyl cyanide
It is preferable to use it in an amount of 20% by weight or less because it accelerates gelation when kneading with the PVC resin, but if it is used in an amount exceeding 20% by weight based on the graft portion, it may cause coloring or even deteriorate moldability. As the graft polymerization initiator, the same initiator as used in polymerizing the acrylic elastomer (A) can be used. Graft polymerization is carried out under normal emulsion polymerization conditions, following the production of the acrylic elastomer (A) latex, or in a separate reactor, by adding an initiator, polymerization regulator, crosslinking agent, etc. as necessary. can be done. In the graft polymerization, the entire amount of each monomer can be added at once, either continuously or discontinuously, to allow the polymerization to proceed. Further, each monomer can be polymerized alone or in a mixture in one stage or in multiple stages. The obtained latex of the graft copolymer is usually coagulated by salting out or acidic precipitation, washed with water, dried, and can be recovered in the form of a powder. The resin composition of the present invention consists of 3 to 30 parts by weight of the graft copolymer (B) thus obtained and 97 to 70 parts by weight of the vinyl chloride polymer, totaling 100 parts by weight.
If the graft copolymer (B) is less than 3 parts by weight, the effect of improving impact resistance will be small, and if it exceeds 30 parts by weight, the excellent mechanical properties originally possessed by vinyl chloride resin will be impaired, such as a decrease in tensile strength. Undesirable. As the vinyl chloride polymer, in addition to polyvinyl chloride, a vinyl chloride copolymer containing 70% by weight or more of vinyl chloride can also be used. Examples of vinyl chloride comonomers used include ethylene, propylene, vinyl bromide, vinylidene chloride, vinyl acetate, acrylic esters, and methacrylic esters. The graft polymer (B) and the vinyl chloride polymer are preferably mixed in powder form using, for example, a ribbon blender, a Henschel mixer, and a known kneading machine such as a mixing roll, a Banbury mixer, an extruder, and an injection molding machine. It is molded by etc. During mixing, known stabilizers, plasticizers, lubricants, colorants, etc. may be added as necessary. The present invention will be explained in more detail with reference to Examples below. Note that parts and % in the following examples mean parts by weight and % by weight, respectively. Example 1 (A) Production of acrylic elastomer latex 180 parts of ion-exchanged water purged with nitrogen was placed in a reaction vessel, and 0.45 parts of boric acid and anhydrous sodium carbonate were added.
0.045 parts, potassium oleate 1.5 parts, potassium persulfate
Dissolve 0.15 parts of n-butyl acrylate and 0.25 parts of divinylbenzene while maintaining at 70℃.
of the mixture was added dropwise over a period of 2 hours.
After the dropwise addition was completed, the temperature was kept at the same temperature for 1 hour to complete the polymerization. The polymerization rate was 98%, the average particle size of the latex was 0.20μ, and the pH of the system was
It was 7.5. A mixture consisting of 49 parts of n-butyl acrylate and 1 part of triallyl isocyanurate was further added dropwise to this latex over a period of 2 hours while maintaining the temperature at 70°C, and the state was maintained for 1 hour after the completion of the dropwise addition to complete the polymerization. I let it happen. Polymerization rate is 99%
The average particle diameter of the obtained acrylic elastic body is
0.23μ, and the pH of the system was 7.2. Table 1 shows Examples 1-1), 2), and
3), 4), and as a comparative example, cases in which acrylic elastic material was polymerized in one step were shown in 1), 2),
3). (B) Production of graft copolymer 100 parts of the acrylic elastomer latex obtained in (A) (as polymer solid content), ion-exchanged water
Charge 100 parts of sodium formaldehyde sulfoxylate, 0.2 parts of sodium formaldehyde sulfoxylate, and 0.5 parts of potassium oleate into a reaction vessel, keep at 70°C, and add 25 parts of methyl methacrylate, 10 parts of styrene, and 5 parts of acrylonitrile.
A mixed solution of 0.15 parts of cumene hydroperoxide and 0.15 parts of cumene hydroperoxide was added dropwise over 90 minutes, and after the addition was completed, the temperature was maintained at the same temperature for 1 hour to complete the polymerization. Then 20 parts of methyl methacrylate, cumene hydroperoxide
0.07 part of the mixed solution was added dropwise over 1 hour to advance the polymerization, and after the addition was completed, the temperature was maintained at the same temperature for 1 hour to complete the polymerization. The polymerization rate was 98% or more, and the particle size of the obtained graft copolymer was 0.28μ. This graph latex was added to an aqueous sulfuric acid solution, solidified by acid precipitation, washed, dehydrated, dried, and recovered as a powder. (C) Production of vinyl chloride resin composition 13 parts of the graft copolymer obtained in (B) above and 87 parts of vinyl chloride resin with an average degree of polymerization of 700, total 100 parts
2.5 parts of dibutyltin malate, 0.8 parts of butyl stearate, and 0.7 parts of a lubricant were added to the mixture, and the mixture was heated to 115° C. in a Henschel mixer to obtain a homogeneous mixture. After kneading this vinyl chloride resin composition for 3 minutes using a mixing roll adjusted to 175°C, the resulting sheet was heated and pressed to prepare a test piece, and its impact strength was measured. The impact strength is
A V-notched Izo impact test was conducted in accordance with ASTMD-256. The blending conditions and molding conditions of this vinyl chloride resin composition are set to low slip conditions. 13 parts of the graft copolymer obtained in the above (B), 87 parts of vinyl chloride resin with an average degree of polymerization of 700, a total of 100 parts, 2.0 parts of tribasic lead sulfate, 0.3 parts of dibasic lead stearate, and 2.0 parts of lead stearate. 1 part and 0.3 part of stearic acid and heated at 115°C in a Henschel mixer.
A homogeneous mixture was obtained. This vinyl chloride composition was molded into a square bar using a 30 mmφ single screw extruder under the following conditions. Temperature Cylinder 1 Cylinder 2 150℃ 165℃ Cylinder 3 Die 180℃ 200℃ Screw CR=3.0, 30mmφ full-flight screw The impact strength of the molded product was measured according to ASTM D-256 using the U-notched Izo impact test. . The blending conditions and molding conditions of this vinyl chloride resin composition are set to be highly slippery conditions. Table 1 shows the measurement results for impact strength, weather resistance, and moldability under low and high slip conditions. The weather resistance and moldability were evaluated using the methods shown below. Weather resistance: Weatherometer (WE-type manufactured by Toyo Rika)
The Izot impact strength and degree of coloring are shown after accelerated exposure treatment. Judgment of degree of coloring ○...No coloring △...Slightly colored ×...Coloring Moldability: Appearance uniformity and gloss of the molded product were judged with the naked eye. ○...Good △...Slightly poor ×...Poor

[Table] Example 2 Operate in the same manner as Example 1 (A), except that the 1st and 2nd stages
Five types of acrylic elastic bodies were manufactured by changing the ratio of the rows. Divinylbenzene was used as the crosslinking agent in the first stage, and triallylisocyanurate was used as the graft crosslinking agent in the second stage. Table 2 shows the evaluation results of the vinyl chloride resin composition obtained in the same manner as in Example 1. Table 2 also shows Comparative Examples 4) and 5).

[Table] Example 3 In Example 1 (A), an acrylic elastic latex was obtained using 2-ethylhexyl acrylate instead of butyl acrylate as the acrylic acid alkyl ester. Six types of graft copolymers were obtained by changing the ratio of monomers during graft polymerization of 60 parts of the monomer mixture to 100 parts of this acrylic elastomer latex (as polymer solid content). The additional emulsifier, catalyst system, etc. used were the same as in Example 1(B). The evaluation results of PVC resin compositions obtained by operating these graft copolymers and PVC resins in the same manner as in Example 1(C) are shown in Table 3 together with comparative examples. The proportions of monomers to be graft-polymerized in Table 3 are expressed in % by weight relative to the graft portion.

[Table] Example 4 An acrylic elastic latex was obtained in the same manner as in Example 1(A) except that octyl acrylate was used as the acrylic acid alkyl ester instead of butyl acrylate. This acrylic elastic material
Five types of graft copolymers were obtained by changing the amount of the monomer mixture to be graft-polymerized to 100 parts (as solid content). However, as an additional emulsifier, 0.75% of potassium oleate was used with respect to the monomer mixture to be graft-polymerized. As polymerization catalysts, sodium formaldehyde sulfoxylate and tert-butyl hydroperoxide were used in an amount of 0.3% and 0.35%, respectively, based on the monomer mixture to be graft-polymerized. The ratio of each monomer in the graft polymerized monomer mixture is 75% methyl methacrylate, 15% styrene, and 10% acrylonitrile. The evaluation results of PVC resin compositions obtained by operating these graft copolymers and PVC resins in the same manner as in Example 1(C) are shown in Table 4 together with comparative examples.

[Table] Example 5 As a comparative example, methyl methacrylate-butadiene-styrene resin (MBS resin) or chlorinated polyethylene (ClPE), which is a commercially available vinyl chloride resin modifier, was used to improve the polymerization of Example 1(C). Table 5 shows the results of measuring the weather resistance of the vinyl chloride resin composition produced under slippery conditions and the vinyl chloride resin composition of Example 1-1) of the present invention under highly slippery conditions. .

[Table] As is clear from the comparison of the above Examples and Comparative Examples, the vinyl chloride resin composition of the present invention has high impact resistance over a wide range of molding conditions, from low lubricity conditions to high lubricity conditions. It exhibits strength, and also has excellent weather resistance and moldability.

Claims (1)

[Scope of Claims] 1 3 to 30 parts by weight of the following graft copolymer (B) and 97 to 70 parts by weight of a vinyl chloride polymer or a vinyl chloride copolymer containing 70% by weight or more of vinyl chloride (total amount
100 parts by weight) of a vinyl chloride resin composition with good weather resistance, impact resistance, and moldability. (i) 99.9 to 99.2% by weight of acrylic acid alkyl ester having 2 to 10 carbon atoms in the alkyl group
30-70% mixture of 0.1-0.8% by weight of cross-linking agent and
Part by weight is emulsion polymerized to form a polymer having rubber elasticity, (ii) in the presence of this emulsion polymer, 2
70 to 30 parts by weight of a mixture consisting of 99 to 97% by weight of an acrylic acid alkyl ester having ~10 carbon atoms and 1 to 3% by weight of a polyfunctional grafting agent having one or more allyl groups (provided that (i ) and (ii) (with the total amount of components being 100 parts by weight),
An acrylic elastic material (A) having a two-layer structure with different crosslinking densities is formed, with the inner layer having a low crosslinking density and the outer layer having a high crosslinking density; (iii) methacrylic acid is added to 100 parts by weight of this acrylic elastic material (A) Graft polymerization of 25 to 125 weight % of a monomer or monomer mixture consisting of 100 to 60 weight % of an alkyl ester, 40 to 0 weight % of an aromatic vinyl compound, and 20 to 0 weight % of a vinyl cyanide compound in one or multiple stages. graft copolymer (B).