JPH0453860A - Methacrylate resin composition - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention provides a method for improving mold releasability during injection molding, which is composed of a methyl methacrylate copolymer and a specific amount and composition of a glycerin higher aliphatic monoester. The present invention relates to a methacrylic resin composition that is excellent and gives molded products a good appearance.

[Prior art]

Conventionally, in the molding of methacrylic resin compositions, there was no need for active mold release formulations because there were no problems with mold release that would hinder industrial implementation. So-called external mold release agents, which are applied to molded parts, have not usually been used because they may impair the aesthetic appearance of molded products.

However, in recent years, with the introduction of robotization in methacrylic resin molding, molded products have come to be handled mechanically during the resin molding process, so technology that provides good mold release properties is one of the effective means for improving productivity. In the case of ultra-mirror mold molding for optical lenses and optical discs, long-shaped resin is required to achieve extremely high adhesion between the molded product and the mold surface. In order to obtain molded products with high-precision surfaces, such as lenses, molding is performed using ultra-high pressure injection molding machines, but in this case, it is relatively difficult to release the mold from the mold, so long-forming materials are used. From the perspective of the need for
There has been an increasing demand for methacrylic resin molding materials with excellent mold release properties.

Conventionally, liquid paraffin, wax, higher fatty acids and their esters, higher aliphatic alcohols, etc. have been known as mold release agents.

However, when trying to use these additives in a slurry polymerization system such as a suspension method, acidic additives make the polymerization system extremely unstable, and neutral additives cannot be added in excess of a certain amount. However, the mold releasability did not improve as much as expected. Another major problem was that the external appearance deteriorated because the polymerization aids and other additives such as a mold release agent were used in combination.

When casting methyl methacrylate copolymer, polyhydric alcohols, fatty acid esters, fatty acids (
and Ami 1), a method of obtaining a polymerization product by mixing an aliphatic metal salt, etc. into a monomer is disclosed (Japanese Patent Application Laid-Open No. 61-7
3754). However, in this method, the concentration of the mold release agent to obtain a satisfactory mold release effect is 1000 to 20000 p.
pm, which causes undesirable changes in physical properties such as a decrease in heat distortion temperature.

Furthermore, since this method limits the types of methacrylic resin moldings that can be obtained, it does not necessarily contribute to improving the mold releasability of injection molded products.

Furthermore, higher fatty acids such as stearic acid and metal stearate and their metal salts are known to have good mold release effects, but they have caused a serious problem in that they significantly corrode metal surfaces.

Furthermore, with the aim of improving the releasability of methacrylic resin molded products, we improved the mold releasability during cast molding by devising the shape of the casting mold when obtaining methyl methacrylate copolymer by cast polymerization. A method of improvement is disclosed. (Opening hours 61-222708, opening hours 6l-222709),
However, since such improvements are limited to methods for obtaining extremely specific molded products, it has been difficult to claim that a substantial improvement in mold releasability has been achieved.

Additionally, a method of adding glycerin higher fatty acid esters and saturated aliphatic higher alcohols has been disclosed in order to improve mold releasability during injection molding (JP-A-1-294
However, even with this method, the improvement in mold releasability was still insufficient (furthermore, it was observed that silver streaks appeared on the surface of the injection molded product in some cases).

[Problem to be solved by the invention]

The present inventors have overcome the drawbacks of the conventional mold release property imparting formulations as described above, and the mold release property during injection molding is significantly improved, and the generation of silver streaks on the surface of the molded product is suppressed. Furthermore, the inventors have discovered a methacrylic resin composition that is comparable in mechanical strength, heat resistance, etc. to conventional products, leading to the present invention.

[Means to solve the problem]

That is, the present invention relates to a methacrylic resin composition comprising a methyl methacrylate copolymer and 500 ppm to 5000 ppm of a glycerin higher fatty acid monoester represented by the following general formula (1), and relates to a C11-0 −
and -R SaH-0-H (1) 昌2-O-H R4: Alkyl having 10 to 30 carbon atoms, and an alkyl in which the ratio of alkyl having 18 carbon atoms is 80 to 99%; 500-3000ppm stearyl alcohol
The present invention relates to the above-mentioned methacrylic resin composition containing the above-mentioned methacrylic resin composition.

The glycerin higher fatty acid monoester, which is a component of the resin composition of the present invention, is represented by the following general formula (1), where R1: alkyl having 10 to 30 carbon atoms; In alkyl R1 where the ratio of alkyl having number 18 is 80 to 99%, the ratio of alkyl having carbon number 18 is 80%
It is important that it be ~99%. If this ratio is less than 80%, not only the mold releasability is poor, but also silver streaks are likely to occur on the surface of the molded product. On the other hand, if this ratio exceeds 99%, clouding tends to occur on the mold surface, and therefore,
There is a problem that cloudiness is transferred to the surface of the molded product. Moreover, glycerin higher fatty acid monoesters with this ratio exceeding 99% are not produced industrially. Even if this product were to be manufactured, it would be very expensive and would have a significant cost disadvantage as an additive for general-purpose resins. The preferred ratio is 85-99%.

It is not clear why when the ratio of alkyl having 18 carbon atoms is 80 to 99%, the effect of improving mold releasability, suppressing silver streaks, and suppressing clouding of molded products is so remarkable. It is presumed that one reason is that the polarity of the glycerin higher fatty acid monoester changes due to the change in the number of carbon atoms, and as a result, the compatibility with the methacrylic copolymer changes.

Moreover, the content is in the range of 500 to 5000 ppm, preferably 700 to 3000 ppm. When this content is less than 500 ppm, the mold release effect is significantly reduced, and when it is used in excess of 5000 ppm, the mold release property of the resin composition is good, but the heat deformation resistance is reduced.
In addition, the mold surface is severely contaminated due to bleeding of additives from the resin.

Generally, industrially produced glycerin higher fatty acid monoester contains several percent of diesters and triesters as impurities, but this amount will not impair the characteristics of the composition of the present invention. do not have.

In addition, 500 to 3000 pp of stearyl alcohol
The composition of the present invention containing m maintains the characteristics of excellent mold releasability and molded product appearance, and also has good molding processability. If this amount is less than 500 ppm, no effect of improving molding processability will appear, and if it exceeds 3000 ppm, heat deformation resistance will deteriorate, which is undesirable. Preferably 75
It is 0 to 2000 ppm.

The methyl methacrylate copolymer in the composition of the present invention refers to a copolymer consisting of a methyl methacrylate unit as a main unit and a monomer unit copolymerizable with the methyl methacrylate unit. The content of methyl methacrylate units is preferably 70% by weight or more. Examples of copolymerizable monomer units include methyl acrylate units, ethyl acrylate units, butyl acrylate units, isobutyl acrylate units, 2-ethylhexyl acrylate units, cyclohexyl methacrylate units, and butylcyclohexyl methacrylate units. preferable. The content of these monomer units in the copolymer is preferably 0.5% by weight or more and less than 30% by weight. If it is less than 0.5% by weight, the thermal decomposition behavior during molding will be severe, and if it is more than 30% by weight, it will cause a significant decrease in heat deformation resistance, which is not preferable. The weight average molecular weight is preferably 50,000 to 500,000, preferably 50,000 to 300,000, more preferably 60,000 to 200,000.

The methyl methacrylate copolymer can be produced by commonly used polymerization methods such as cast polymerization, bulk polymerization, suspension polymerization, solution polymerization, and emulsion polymerization. When performing solution polymerization, a solution prepared by dissolving a monomer mixture in an aromatic hydrocarbon solvent such as toluene or ethylbenzene can be used. When polymerizing by suspension polymerization or emulsion polymerization, water can be used as a medium. When polymerizing by bulk polymerization,
Polymerization can be initiated by free radicals generated by heating or by irradiation with ionizing radiation, as is commonly done.

As the initiator used in the polymerization reaction of the copolymer of the present invention, any initiator generally used in radical polymerization can be used, such as azo compounds such as abbis isobutyl nitrile, hensyl peroxide, lauroyl Organic peroxides such as peroxide and tert-butylperoxy-2-ethylhexanoate are used, and especially when polymerization is carried out at a high temperature of 90°C or higher, solution polymerization is common. Therefore, peroxides, azobis initiators, etc. whose 10-hour half-life temperature is 80°C or higher and are compatible with the organic solvent used are preferred.
, 1-bis(t-butylperoxy)33゜5-trimethylcyclohexane, cyclohexanone peroxide,
2,5-dimethyl-2,5-di(-.

hexane, 1,1-azobis(
Examples include 1-cyclohexanecarbonitrile), 2-(carbamoyl anionisobutyronitrile), etc. These initiators are used in a range of 0.005 to 5% by weight.Polymerization of the copolymer of the present invention Q required for the reaction The molecular weight regulator used accordingly is any one used in radical polymerization, such as butyl mercaptan, octyl captan, dodecyl mercaptan,
Particularly preferred are mercaptan compounds such as 2-ethylhexyl thioglycolate. These molecular M regulators are added in a concentration range such that the degree of polymerization of the copolymer is controlled within the above range.

Methods for adding glycerinia higher fatty acid monoester to the composition of the present invention include a method in which it is dissolved in 1,000 pieces and then polymerized as a homogeneous solution;
Alternatively, there is a method of post-adding (7) kneading to a pellet-shaped copolymer.In order to effectively express the effect of glycerin higher fatty acid monoester, the post-adding method is preferable.The reason for this is not clear, but It is presumed that the dispersion state of glycerin higher fatty acid monoester, chemical alteration, etc. are involved.

In addition, the composition of the present invention may contain known additives such as lubricants, antioxidants, etc., to the extent that their properties are not impaired. Antistatic agents, ultraviolet absorbers, etc. can be added.

(Example) Various analyzes and physical property evaluations of copolymers and compositions thereof were performed by the following methods.

(1) Monomer unit decomposition in copolymer Each constituent unit was quantified by pyrolysis gas chromatography at a furnace temperature of 450°C.

(2) Weight average molecular weight The weight average molecular weight of the copolymer was measured by gel permeation chromatography (GPC). GPC measurement is performed by dissolving a certain amount of the copolymer in tetrahydrofuran (
30■/30d) Prepare the sample solution and measure it using PMMA based on the calibration curve obtained from the standard polychishino.
The value was obtained by converting it into .

(3) Quantification of Glycerin Higher Fatty Acid Monoester After dissolving a certain amount of the resin composition in acetone, the polymer component is reprecipitated with methanol. After the polymer was filtered off, the solution was evaporated to dryness and reacted with BAS (bistrimethylsilylacetamide) using pyridine as a solvent. A certain amount of an internal standard substance was added to the resulting product, followed by GC and analysis.

(4) Heating distortion temperature (l(DT)) Measurement was carried out based on ASTM-0648.The test piece was annealed at 96°C for 2 hours, and then adjusted to 48°C at 23°C and 52% relative humidity. time).

(5) Moldability (MFI) AST? Method ■ of I 01238 (230°C13,8k
g), MFI (g/10 min) was measured.

(6) Evaluation of M-type property A 4-stage plate mold as shown in Figure 1 was attached to a 3oz injection molding machine, and the molding temperature was 250' (1. The mold temperature was 50°C and the injection pressure was 920 kg/crA. When molding was performed under these conditions, products that developed cracks, chips, or cracks during four-stage plate molding were considered to be defective products, and the percentage of defective products among all molded products was defined as the defect incidence rate.

The total number of samples was 20 to keep the injection molding conditions constant.
After shot molding, 1005 hot molding was performed. Therefore, the total number was evaluated as -100.

In addition, when molding, Perenoto is dried and the moisture content is 0.
．． It was used in an amount of 0.6% by weight or less.

(7) Silver streak evaluation Among the same molded products that were subjected to mold releasability evaluation, those with silver streaks observed on the surface are considered to be defective products, and the percentage of defective products in all molded products is defined as the defective incidence rate. did.

(8) Evaluation of mold surface cloudiness (6), (7) After molding the molded product for evaluation, the surface of the mold was visually observed, and the degree of cloudiness was ranked.

◎ No cloudiness ○ Almost no cloudiness △ Cloudy × Significant cloudiness Example 1 Contents: 5700 g of pure water in a 1 ton, 13 ff glass separable flask, 28.5 g of tribasic calcium phosphate as a suspension stabilizer, 0.23 g of sodium lauryl sulfate.
After dispersing g, 3705 g of methyl methacrylate,
95 g of methyl acrylate, 5.7 g of 7-bisisobutyroni[-ril, and 9.9 g of n-octyl mercaptan.
A mixed solution consisting of was added, and polymerization was carried out at 80°C with stirring.

Next, the polymerization system was cooled to room temperature, and the contents were filtered, washed with water, and dried to obtain a colorless bead-like polymer.

The obtained bead-like polymer was extruded using a Ghent-type twin-screw extruder with a screw diameter of 30 mm.
1000 ppm each of higher fatty acid monoglyceride 1- and stearyl alcohol in which the ratio of alkyl having 18 carbon atoms is 85% in R6 to the bead-like polymer
Each was blended and extruded.

The resin composition obtained here was in the form of pellets, and its general physical properties and mold release properties were evaluated using the methods described above. These results are shown in Tables 1 and 2.

Examples 2 to 6, Comparative Examples 1 to 5 The same procedure as in Example 1 was carried out except that the composition and addition amount of stearyl alcohol and higher fatty acid monoglyceride were changed. The results are shown in Tables 1 and 2.

Example 7 Menal methacrylate 68% by weight, methyl acrylate 2% by weight, ethylhenzea 30% by weight, Ll.
Butyl peroxidation/3.3.5-)limethylcyclohexane 300 ppm and n-octyl mercaptan 800
A mixed solution consisting of
After polymerization was carried out for 20 minutes, the volatile components were removed by reducing the pressure in a storage tank connected to the polymerization reaction tank, and then the mixture was continuously transferred in a molten state to an extruder. Here, stearyl alcohol 1 is added from the additive inlet connected to the extruder.
000 ppm and R1, 1000 ppwl of higher fatty acid monoglyceride in which the proportion of alkyl having 18 carbon atoms is 85% was dissolved at 90°C and quantitatively fed in four forms to form the resin composition into pellets. I got it from The obtained pellet-shaped resin composition was subjected to the same evaluation method as in Example 1. These results are shown in Tables 1 and 2.

Example 8 In Example 1, the monomer was methyl methacrylate 3050
Example 1, except that 150 g of methyl acrylate and 600 g of t-butylcyclohexyl methacrylate were used.
I did exactly the same thing.

The results are shown in Table 1 and Table 2.6.

Below is a blank monomer table (!7 (iit glycerin martyrdom tree alliance 1 saving ester) * MMA: Methyl methacrylate * MA ・Methyl acrylate * t-BCMMA ・ t-phthyl methacrylate Chlorohexynol (Effects of the invention) According to the present invention, the mold releasability during injection molding is significantly improved, the occurrence of silver streaks on the surface of the molded product is suppressed, and the mechanical strength, heat resistance, etc. are improved compared to conventional products. A comparable methacrylic resin composition can be obtained.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of mold releasability evaluation. Patent applicant: Asahi Kasei Industries, Ltd. Complete now 1ill solid a-5 L Nh, Koshishi

Claims (1)

[Claims] 1. Methyl methacrylate copolymer and the following general formula (1
) Glycerin higher fatty acid monoester 50
A methacrylic resin composition comprising 0 ppm to 5000 ppm. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (1) R_1: Alkyl having 10 to 30 carbon atoms, and
The methacrylic resin composition according to claim 1, which contains alkyl 2 having a carbon number of 18 in a ratio of 80 to 99%, and stearyl alcohol in an amount of 500 to 3000 ppm.