JPS6225699B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a resin composition, and more specifically, to a resin composition that is colorless and transparent and has excellent mechanical strength and heat resistance. In recent years, there has been an especially strong demand for resins that have excellent heat resistance, mechanical strength, and hot water whitening resistance, and are also colorless, transparent, and inexpensive for applications such as microwave tableware, light electrical parts, and medical equipment. be. Conventional technology By the way, among resins that are easy to injection mold, styrene-maleic anhydride copolymer is a colorless and transparent resin that has excellent heat resistance and can be supplied at low cost. Although it is commercially available, it has the disadvantage of whitening in hot water of 100°C or higher. On the other hand, styrene-methacrylic acid copolymer (hereinafter referred to as
SMAA resin (abbreviated as SMAA resin) is a transparent heat-resistant resin that does not whiten even when treated in hot water at 100°C, and can be supplied at low cost, and various disclosures regarding its manufacturing method and properties have been published (US Patent No. 3035033). No. specification,
(Japanese Patent Application Laid-open No. 161409/1983). However, this
SMAA resin is extremely susceptible to cracks in its injection molded products [Kobunshi Kagaku, 26 ,
883, (1969)], so it has not yet been commercialized. In addition, an SMAA resin composition that improved the occurrence of such cracks was proposed (Japanese Patent Application Laid-Open No. 1983-1999).
96641), but even this method is not necessarily fully satisfactory in terms of crack occurrence. The inventors previously
It was discovered that SMAA resin can be blended extremely well with methyl methacrylate-based copolymers, and as a result, mechanical strength can be greatly improved (Japanese Patent Laid-Open No. 56
-98251). However, even with this method of blending, it was not possible to prevent the occurrence of cracks. As described above, although SMAA resins can be supplied at low cost, no one with sufficiently satisfactory performance has been found so far. Problems to be Solved by the Invention In view of the above circumstances, the inventors have
We have conducted extensive research in order to take advantage of the characteristics of SMAA resin and improve the above-mentioned drawbacks in order to provide a colorless and transparent resin composition that has excellent mechanical strength and heat resistance, and can also provide molded products that do not generate cracks. As a result, a copolymer consisting of an aromatic vinyl compound unit and a methacrylic acid unit was combined with a specific copolymer containing a methyl methacrylate unit, a polymer block of an aromatic vinyl compound, and a polymer block of a conjugated diene compound. discovered that a resin composition formed by combining copolymers consisting of
Based on this knowledge, we have completed the present invention. Means for Solving the Problems That is, the present invention provides (A) 70 to 97% by weight of aromatic vinyl compound units and 3 to 30% by weight of methacrylic acid units.
(B) a copolymer consisting of a methyl methacrylate unit and an alkyl acrylate unit or an aromatic vinyl compound unit or both units; and (C) a polymer block of an aromatic vinyl compound. A composition comprising a copolymer comprising a polymer block of a conjugated diene compound and a copolymer having a content of the polymer block of an aromatic vinyl compound of 60 to 95% by weight, the component (A) , heat resistance characterized in that the content of component (B) and component (C) is 40 to 98% by weight, 1 to 40% by weight, and 1 to 20% by weight, respectively, based on the total amount of those components. A resin composition is provided. The copolymer of component (A) used as the main component in the resin composition of the present invention is an aromatic vinyl compound unit.
It has a carboxylic acid group consisting of 70 to 97% by weight and 3 to 30% by weight of methacrylic acid units, and has significantly improved heat resistance. If the content of methacrylic acid units is less than 3% by weight, the heat resistance will not be improved sufficiently and the compatibility with the copolymer of component (B) will decrease, and if the content exceeds 30% by weight, heat resistance will be insufficient. Stability is reduced and melt flowability is significantly reduced. Examples of the aromatic vinyl compound unit include units such as styrene, α-methylstyrene, p-methylstyrene, dimethylstyrene, p-tert-butylstyrene, and chlorostyrene.
In particular, styrene units are preferred. The copolymer used as component (B) in the resin composition of the present invention consists of methyl methacrylate units, alkyl acrylate units, aromatic vinyl compound units, or both units, and by containing this, , the mechanical strength of the resin composition is improved. Such a copolymer usually contains 30 to 99.5% by weight of methyl methacrylate units, 0 to 70% by weight of aromatic vinyl compound units, and 0 to 20% by weight of alkyl acrylate units. In this copolymer, if the content of alkyl acrylate units exceeds 20% by weight, the heat resistance of the copolymer will decrease, and if the content of aromatic vinyl compound units exceeds 70% by weight, the copolymer will be reduced in heat resistance. The mechanical strength of the polymer decreases, which is unfavorable for the resin composition in either case. A preferred copolymer is a methyl methacrylate-alkyl acrylate copolymer consisting of 80-99.5% by weight of methyl methacrylate units and 0.5-20% by weight of alkyl acrylate units, which is polymethyl methacrylate (PMMA). It is commercially available as. Another preferred example of the component copolymer (B) is a methyl methacrylate-aromatic vinyl compound copolymer comprising 30 to 95% by weight of methyl methacrylate units and 5 to 70% by weight of aromatic vinyl compound units. Can be mentioned. Among these copolymers, those in which the aromatic vinyl compound unit is a styrene unit are well known as MS resins. Furthermore, as another preferable example of the component (B) copolymer, 30 to 98.9% by weight of methyl methacrylate units,
A terpolymer of methyl methacrylate-alkyl acrylate-aromatic vinyl compound consisting of 0.1 to 10% by weight of alkyl acrylate units and 1 to 60% by weight of aromatic vinyl compound units may be mentioned. The most common alkyl acrylate units in these copolymers are methyl acrylate units or ethyl acrylate units;
Acrylic acid ester units having the above alkyl groups may also be used. The copolymer used as component (C) in the resin composition of the present invention is composed of a polymer block of an aromatic vinyl compound and a polymer block of a conjugated diene compound, has impact resistance, and contains this copolymer. By doing so, toughness is imparted to the resin composition. Examples of aromatic vinyl compounds that are monomer components of this block copolymer include styrene,
Examples include α-methylstyrene and p-methylstyrene, but styrene is the most common. The content of the polymer block of the aromatic vinyl compound in the copolymer ranges from 60 to 95% by weight. If this content is less than 60% by weight, the compatibility with the (A) component copolymer and (B) component copolymer will decrease, while if it exceeds 95% by weight, the impact resistance of the copolymer will decrease. , the effect of preventing the occurrence of cracks in the resin composition disappears. Moreover, as the conjugated diene compound which is another monomer component of this copolymer, butadiene is most preferable. In the resin composition of the present invention, the copolymer constituting the main part is a copolymer of component (A), which plays the role of imparting heat resistance to the resin composition. On the other hand, the copolymer of components (B) and (C) provides strength, and both copolymers are essential components of the resin composition. In other words, in the combination of (A) component and (B) component, or (A) component and (C) component,
It is impossible to maintain transparency and suppress the occurrence of cracks at the same time, and it is possible to achieve a desirable method without cracks by mixing three types of copolymers of components (A), (B), and (C). A transparent heat-resistant resin is obtained. In the resin composition of the present invention, component (B) and (C)
The content of the component copolymer is necessary to reinforce the strength of the resin composition. The content of component (B) copolymer is in the range of 1 to 40% by weight, preferably 5 to 35% by weight, based on the total weight of component (A), component (B), and component (C). The content of component (C) copolymer is in the range of 1 to 20% by weight, preferably 5 to 15% by weight. (B)
If the content of the component or the content of component (C) is less than 1% by weight, the strength of the resin composition will not be reinforced and cracks will occur, while on the other hand, if the content of component (B) exceeds 40% by weight, Alternatively, if component (C) exceeds 20% by weight, the heat resistance of the resin composition will sharply decrease. Therefore, (A)
The content of the component copolymer is (A) component, (B) component and (C) component.
It ranges from 40 to 98% by weight based on the total weight of the components. The resin composition of the present invention usually contains lubricants such as higher fatty acids typified by stearic acid, higher fatty acid metal salts typified by zinc stearate, higher fatty acid mono-, di-, and triglycerides, and higher fatty acid amides. 0.001-5% by weight based on the composition
It is added within the range of Additionally, if necessary, mineral oil, plasticizers such as dioctyl sebatate, etc. may be added in the range of 0.01 to 5% by weight, and depending on the thermal history of the component (A) copolymer, In order to suppress the formation of intermolecular acid anhydrides due to intermolecular dehydration, higher aliphatic alcohols such as 2-ethylhexyl alcohol, dodecyl alcohol, stearyl alcohol, etc.
It may be added in a range of % by weight. Although various methods can be used to separate and quantify each copolymer in the resin composition of the present invention, the following method is typically used. That is, first, component (C) is separated as a soluble component using a toluene-cyclohexane mixed solvent.
The composition of the separated component (C) copolymer is confirmed using an infrared spectrophotometer. Next, after dissolving the separated components (A) and (B) in methyl ethyl ketone,
It is treated with an aqueous potassium hydroxide solution at ℃ to separate the component (A) copolymer as a potassium salt. Next, the copolymer is recovered under acidic conditions, its weight is confirmed, and the components of the copolymer are confirmed using an infrared spectrophotometer. Finally, the component (B) copolymer is quantified, and the content of methyl methacrylate units, alkyl acrylate units, and aromatic vinyl compound units in the copolymer is determined using pyrolysis gas chromatography. In addition, all the usual radical copolymerization methods can be used to produce the copolymer of components (A) and (B), while the copolymer of component (C) can be produced using an organolithium catalyst. It can be produced by an anionic polymerization method. Effects of the Invention The resin composition of the present invention is colorless and transparent, has excellent mechanical strength and heat resistance, and can provide molded products that do not generate cracks, such as microwave tableware, light electrical parts, and medical instruments. It is suitably used for such purposes. EXAMPLES Next, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these Examples in any way. In addition, the measurement method of each physical property is as follows. (1) Vikatsu softening temperature: ASTM-D1525 (2) Bending strength and bending deflection: ASTM-D790 (3) MFR: 230℃, 3.8Kg load (4) Colorless transparency: Injection molding test with a thickness of 3mm A piece was prepared and observed with the naked eye. (5) Crack occurrence test Test piece: Standard ASTM tensile test piece with dumbbell shape (using an in-line injection molding machine, cylinder temperature within 230-260℃, metal temperature 60℃, shot shot point + 5 kg/ ^cm2 is always 50
Molded at an injection pressure of Kg/ ^cm2 . ) Test method: Apply olive oil, leave at room temperature, and observe. Further, as the component (B) copolymer, the following known resins were used. Copolymer (B) 1 PMMA Consists of 98.5% by weight of methyl methacrylate units and 1.5% by weight of methyl acrylate units, and has a flow index (MFR) (230°C, 3.8 kg load) of 1.9 g/10 min.
PMMA. Copolymer (B) 2 MS resin An MS resin consisting of 65% by weight of methyl methacrylate units and 35% by weight of styrene units, with an MFR (230°C, 3.8 kg load) of 4.2 g/10 minutes and a solution viscosity of 6.3 centipoise. Synthesis Example 1 Copolymer (A) 1 Synthesis of SMAA resin 75.2% by weight of styrene, 4.8% by weight of methacrylic acid, and 20% by weight of ethylbenzene as a liquid mixture, and 1,1-di-tert-butylperoxy as a polymerization initiator. 3,3,5-trimethylcyclohexane was used. This liquid mixture was continuously fed at a rate of 1/hr to a jacketed complete mixing reactor having an internal volume of 2 to carry out polymerization. The polymerization temperature was 136°C. The polymerization reaction solution was continuously taken out and supplied to an unreacted substance degassing device. The obtained polymer was colorless and transparent, and as a result of composition analysis by neutralization titration of this polymer, 92% by weight of styrene units and 8% of methacrylic acid units were found.
It was in weight%. When MFR was measured, it was 5.2g/
It took 10 minutes (230℃, 3.8Kg load). Synthesis Example 2 Copolymer (A) 2 Synthesis of SMAA Resin The following components were supplied to the stainless steel autoclave in step 5. Styrene 1352g Methacrylic acid 338g Water 1.7Kg Hydroxycellulose 1.5g Lauryl mercaptan 9.0g Azodiisobutynitrile 4.5g This mixture was stirred vigorously and heated to 75°C under a nitrogen atmosphere. After 1 hour, increase the temperature to 98℃
The reaction was completed after stirring for 2.5 hours. The product was then cooled, centrifuged, washed with water and dried at 70°C. The resulting bead-like polymer is colorless and transparent.
As a result of composition analysis by neutralization titration of this polymer,
The methacrylic acid units were 19% by weight and the styrene units were 81% by weight. When the MFR was measured, it was 0.9 g/10 minutes (230°C, 3.8 kg load). Synthesis Example 3 Copolymer (C) Synthesis of styrene-butadiene block copolymer Using styrene as the aromatic vinyl compound and 1,3-butadiene as the conjugated diene compound, n
- at least one polymer block consisting of styrene units and at least one polymer consisting of conjugated diene compound units, by a known method of polymerization in hexane, cyclohexane or benzene using butyllithium as a polymerization initiator; Copolymers (C)-1 and (C)-2 having blocks were obtained. The characteristics of these copolymers are shown in Table 1.

[Table] Examples 1 to 8, Comparative Examples 1 to 5 Using each copolymer in the proportions shown in Table 2,
Kneading and extrusion were performed using a twin-screw extruder to obtain a pellet-like mixture. This pellet-like mixture was molded into test pieces using an injection molding machine, and
The bending strength and amount of bending deflection were measured, and the presence or absence of cracks and colorless transparency were also observed. The results are shown in Table 2.

[Table] Comparative Examples 6 to 9 Pellet-like mixtures were obtained in the same manner as Examples 1 to 8 by changing the content of copolymer (C) as shown in Table 3, and then molded into test pieces. , each characteristic was determined. The results are shown in Table 3 together with the results of Examples 1, 4, 5, 8 and Comparative Example 1.

[Table] Examples 9 to 12, Comparative Example 10 As shown in Table 4, copolymer (A) and copolymer
Pellet-like mixtures were obtained in the same manner as in Examples 1 to 8 by changing the type of (C), and then molded into test pieces to determine each property. The results are shown in Table 4 together with the results of Comparative Example 1.

[Table] As can be seen from Tables 2, 3, and 4, the resin composition of the present invention is colorless and transparent, has excellent heat resistance, and also has toughness and is completely crack-free. It is excellent.

Claims (1)

[Claims] 1 (A) A copolymer consisting of 70 to 97% by weight of aromatic vinyl compound units and 3 to 30% by weight of methacrylic acid units, (B) Methyl methacrylate units and alkyl acrylate units or aromatic vinyl compound units or and (C) a copolymer consisting of a polymer block of an aromatic vinyl compound and a polymer block of a conjugated diene compound, and the content of the polymer block of the aromatic vinyl compound is 60 to 60%. A composition comprising a copolymer of 95% by weight, wherein the content of component (A), component (B) and component (C) is 40 to 98% by weight, respectively, based on the total amount of those components. % by weight, 1 to 40% by weight, and 1 to 20% by weight.