JPH0816184B2 - Methacrylic resin composition - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a methacrylic resin composition for injection molding, and more particularly to a methacrylic resin molding material having excellent surface properties and good releasability.

(Prior Art) Since conventional methacrylic resins have excellent weather resistance and mechanical properties, they are used for a variety of applications such as automobile parts such as tail lamps and meter covers, video discs, sunglasses lenses, Fresnel lenses, optical elements such as lenses. Widely used. These molded products are generally obtained by injection molding, injection compression molding, compression molding, etc., especially when obtaining optical elements such as convex lenses, using a highly polished mold to improve dimensional accuracy. It is easy to cause clouding on the mold surface and molded product surface due to the increase in volatile components due to thermal degradation of the resin due to long-term residence in the cylinder of the molding machine for the purpose of decomposition, and decomposition and hydrolysis of the resin However, there has been a problem that defects such as poor mold release due to an increase in polar groups due to the above-mentioned factors tend to occur. In order to prevent these problems, a general methacrylic molding material is usually added with 0.05 to 1.0 parts by weight of a lubricant such as higher alcohols, higher fatty acid esters, and saturated fatty acids having 18 or less carbon atoms. I have.

(Problems to be Solved by the Invention) However, the conventional method of adding the above-mentioned lubricant has insufficient effect, and the added lubricant and other additives migrate to the resin surface, and the mold surface and the molding In the treatment process for the purpose of anti-reflection and surface hardening, the product surface is stained, and a thin film of lubricant and other additives is formed on the molded product surface.
There were problems to be solved such as a decrease in yield.

Accordingly, an object of the present invention is to provide a methacrylic resin composition that maintains excellent optical properties and moldability, which are the characteristics of methacrylic resin, has excellent mold releasability during injection molding, and has no surface contamination of molded articles. To provide.

(Means for Solving the Problem) As a result of intensive studies, the present inventors have found that the above-mentioned object can be achieved only by adding a certain amount of a specific aliphatic mixture to a general methacrylic molding material. The present invention has been completed.

That is, the gist of the present invention is that the intrinsic viscosity at 20 ° C. in chloroform is 0.30 to 1.0 (dl / gr) with respect to 100 parts by weight of a methacrylic resin, 80% by weight of a saturated fatty acid having 20 to 25 carbon atoms. 80-99% by weight of the fatty acid mixture (I) containing the above, glyceride stearate, glyceride behenate and general formula (A) R ₁ COOR ₂ (A) [wherein R ₁ is C _n H _{2n + 1} R ₂ is C _{n + I} H _{2n + 3} (n is 13 to 21)
Represents an integer. ), Or R ₁ is C ₁₇ H ₃₅ , R ₂ is C
H ₃ and C ₄ H ₉ . ] 1 to 20% by weight of at least one fatty acid ester (II) consisting of a compound represented by
A methacrylic resin composition for injection molding, containing 01 to 0.5 part by weight.

(Action) The methacrylic resin used in the present invention refers to methyl methacrylate alone or at least methyl methacrylate and another copolymerizable monomer having an intrinsic viscosity of 0.30 to 1.0 (dl / gr) in chloroform at 20 ° C. At least one selected from monomers
A methacrylic resin obtained by polymerizing a monomer mixture of seeds. Examples of copolymerizable monomers include, for example, acrylates such as methyl acrylate, ethyl acrylate and butyl acrylate, methacrylates such as ethyl methacrylate, cyclohexyl methacrylate, and tribromophenyl methacrylate; Examples thereof include vinyl compounds such as acrylonitrile, methacrylonitrile, styrene and vinyltoluene; acid anhydrides such as maleic anhydride and itaconic anhydride; and maleimide compounds such as O-chlorophenylmaleimide and cyclohexylmaleimide. These may be polymerized by any of the known polymerization techniques such as bulk polymerization, suspension polymerization, emulsion polymerization, and solution polymerization.

The fatty acid mixture (I) containing 80% by weight or more of a saturated fatty acid having 20 to 25 carbon atoms used in the present invention is at least 1 selected from arachidic acid, heneicosanoic acid, behenic acid, tricosanoic acid, lignoceric acid and pentacosanoic acid. A fatty acid mixture containing 80% by weight or more, preferably 90% by weight or more of a saturated fatty acid of a seed, and optionally containing 80% by weight or more of behenic acid, which is a saturated fatty acid having 22 carbon atoms. A mixture of is preferably used.

The fatty acid ester (II) in the present invention means glyceride esters such as stearic acid (mono, di or tri) glyceride, behenic acid (mono, di or tri) glyceride and methyl stearate, butyl stearate, myristin. General formula (A) R ₁ COOR ₂ …… (A) such as myristyl acid salt, stearyl stearate and behenyl behenate [in the formula, when R ₁ is C _n H _{2n + 1} , R ₂ is C _{n + 1} H _{2n +3} (n is 13-21
Represents an integer. ), Or R ₁ is C ₁₇ H ₃₅ , R ₂ is C
H ₃ and C ₄ H ₉ . ] It is the alcohol ester of the fatty acid represented by these. The ratio of the fatty acid mixture (I) and the fatty acid ester (II) added is
(I) 80 to 99% by weight, (II) 1 to 20% by weight, and the content of the aliphatic mixture is 0.01 to 0.5 parts by weight, preferably 0.03 to 0.4 parts by weight based on 100 parts by weight of the methacrylic resin. Parts by weight.

By using a specific amount of the specific aliphatic mixture as described above, the mixture is moderately coordinated on the surface of the fluid resin during injection molding to maintain good mold release properties, and the volatility of the mixture is low. It is possible to provide a methacrylic resin composition that suppresses the generation of mold cloud because it has an appropriate compatibility with the methacrylic resin. Saturated fatty acids having less than 20 carbon atoms have a high volatility and thus do not have a sufficient effect on mold spiders. And it remains on the surface of the mold at the time of release from the mold, causing mold stains and clouding of the molded product, which is not preferable. If the proportion of the fatty acid mixture (I) in the aliphatic mixture is less than 80% by weight, mold stains and cloudiness of the molded product are likely to occur, which is not preferable.

In addition, glyceride stearate and the general formula (A)
The fatty acid ester (II) represented by is difficult to obtain a sufficient effect on the mold stain by itself, but the synergistic effect is recognized when the fatty acid ester (II) is used in combination with the fatty acid mixture (I) at an addition ratio of 1 to 20% by weight. As a result, a remarkable effect was confirmed on the mold stains and the cloudiness of the molded product. For stearic acid glyceride and compounds other than those represented by the general formula (A), for example, esters of fatty acids having an alkyl group having 13 or less carbon atoms have high volatility, and the effect of improving the cloudiness of the molded article is not observed, or unsaturated. Impurity having a bond is unavoidable and thermal stability is low, which causes coloring of the methacrylic resin, which is not preferable.

Further, when the addition amount of the aliphatic mixture is less than 0.01 parts by weight, the mold release performance is insufficient, and the surface layer of the molded article is likely to peel or crack, while the addition amount is 0.5 parts by weight. If it exceeds, excess fatty acid will adhere to the mold surface,
It is not preferable because it causes generation of mold cloud and surface cloud of the molded product and a decrease in yield during secondary processing such as surface treatment of the molded product.

As a method of mixing the fatty acid mixture used in the present invention into the methacrylic resin, a method of dissolving in a monomer before polymerization and pelletizing a polymer obtained by polymerizing by a known polymerization method with an extruder, or Powdered polymer obtained by pre-polymerization or sheet-shaped polymer is pulverized with a pulverizer and added to the pulverized product, and thoroughly mixed with a Henschel mixer, tumbler, etc., and then pelletized with an extruder. Any method such as a method may be used.

If necessary, additives such as an antioxidant, an ultraviolet absorber, a heat stabilizer and a colorant can be added to the methacrylic resin composition obtained in the present invention.

The methacrylic resin composition obtained as described above,
It has excellent releasability during injection molding and does not stain the surface of the molded product, so it has excellent properties as a molding material and can be used as various optical elements.

(Examples) Next, the present invention will be described in detail with reference to Examples, but the present invention is not limited thereto. All "%" and "parts" in the examples represent "% by weight" and "parts by weight". In addition, the evaluation of the mold cloud in the examples,
The releasability and the surface property of the molded product are evaluated in the following (1) to
It carried out by the method of (3).

(1) Mold Kumori 200L × 70W × 3.2t with a gate in the longitudinal direction of the rectangle
Using an N70A type injection molding machine (manufactured by Japan Steel Works, Ltd.) with a flat plate (mm) set, the mold surface temperature is 50 ° C, the cylinder temperature is 25 ° C, and the primary injection time is 5 seconds. The resin was injected up to 75% of the cavity area, and the number of injections of the mold cloud was measured at the boundary surface of the filled resin tip.

(2) Releasability A pressure sensor is built into the mold opening hydraulic circuit, in which a box mold of length 100 x width 75 x depth 45 x plate thickness 1 (mm) is set.
Using an injection molding machine (IS60B; made by Toshiba Machine Co., Ltd.) that can detect the mold opening pressure applied when opening the mold through the amplifier, molded product under the conditions of mold temperature 60 ℃, cylinder temperature 240 ℃, and cooling time 20 seconds. The mold opening pressure at a weight of 52.5 gr was measured. The pressure sensor used was the PG210KU type (Kyowa Denki Co., Ltd.).
Manufactured by Hunkar Laboratories
Inc.).

(3) Molded product surface property Using an injection molding machine (Neomat 350/120; manufactured by Sumitomo Heavy Industries, Ltd.) with a convex lens mold having a diameter of 100 and a maximum wall thickness of 10 (mm), a mold temperature of 40 ℃, cylinder temperature 230
Molded under conditions of ℃, injection pressure holding time 200 seconds, cooling time 200 seconds, the resulting convex lens molded product is visually observed with reflected light,
The presence or absence of oily stain and the state of delamination of the gate portion was confirmed. Next, this molded product is installed in a vacuum evaporator, and the degree of vacuum is reduced.
Conditions of 10 ^-5 Torr Fluoride magnesium (MgF ₂ ) was vapor-deposited to an optical film thickness of 700 Å, and then 1 mm-spaced cells were formed on the vapor-deposited surface.
100 pieces were cut, and a tape peeling test was performed to evaluate the adhesion. Here, 100/100 indicates that all are in close contact with each other, and 75/100 indicates that 25% of 100 squares have been separated.

The abbreviations of the monomers and additives used in the examples are as follows.

NMA Methyl methacrylate MA Methyl acrylate EA Ethyl acrylate CHMI N-Cyclohexylmaleimide TBPMA Tribromophenyl methacrylate CHMA Cyclohexyl methacrylate ST Styrene Additive A Behenic acid 85%, Araquinic acid 10%
(Brand name: Lunac BA; Kao Corporation) Additive B Araquinic acid 95% (Reagent: Wako Pure Chemical Industries, Ltd.) Additive C Lignoceric acid 95% (Reagent;
Wako Pure Chemical Industries, Ltd. Additive D Stearic acid 97% (Trade name: Lunack 98; Kao Corporation) Additive E Behenic acid 65%, Stearic acid
22% (NAA222; NOF Corporation) Additive F Montanic acid 95% (Reagent; Wako Pure Chemical Industries, Ltd.) Additive G Stearic acid monoglyceride
(Excel T95; Kao Corporation) Additive H Butyl stearate (Exepearl BS; Kao Corporation) Additive I Behenyl Behenate (Exepearl BB; Kao Corporation) Additive J Methyl laurate (Exepearl ML-98) Kao Corporation Example 1 75 MMA21.17 kg, MA0.43 kg, azobisisobutyronitrile 0.022 kg, octyl mercaptan 0.043 in a pressure resistant reactor.
32.4 kg of deionized water prepared by preliminarily dissolving 150 kg of a monomer mixture in an aqueous solution of sodium polymethacrylate, 100 gr of disodium hydrogen phosphate and 3 gr of sodium dihydrogen phosphate.
Then, the mixture was polymerized at 80 ° C, and after the exothermic peak, the mixture was heated at 120 ° C for 1 hour for polymerization. Additive A was added to 100 parts of the obtained powdery polymer.
0.2 part and additive G 0.02 part were added, mixed with a Henschel type mixer, and pelletized with an extruder having a cylinder diameter of 40 mm. The pellets thus obtained were evaluated according to the above-described evaluation method. As a result, no mold cloud was observed at 100 injections, and the mold release resistance pressure was about half of the usual value. No oily stains or delamination was observed on the appearance of the molded product, the peeling test of the MgF ₂ vapor deposition film was 100/100, the adhesion was good, and the methacrylic resin had good mold releasability without mold clouding. A resin composition was obtained.

Comparative Example 1 0.2 part of Additive G was mixed with the methacrylic powdery polymer obtained in the same manner as in Example 1, pelletized in the same manner as in Example 1, and evaluated in the same manner as in Example 1. As a result, the mold cloud was generated when the number of injections was 10, and the mold release resistance pressure was determined in Example 1.
It was about twice as expensive. In addition, oily stains were observed near the gate of the convex lens-shaped molded product, and the adhesion of the deposited film was 85/100. When these are compared with Example 1 as described above,
The results of Example 1 were far inferior in terms of mold cloudiness, releasability and surface property.

Examples 2-7, Comparative Examples 2-6 The composition of the methacrylic resin is MMA 90% -MA 10%, MMA, respectively.
95% -EA5%, MMA90% -CHMI10%, MMA80% -TBPMA20
%, MMA70% -CHMA30%, MMA70% -ST30% of a powdery polymer was obtained in the same manner as in Example 1, and the types and amounts of the additives shown in Table 1 were added. After obtaining pellets by the same method as above, evaluation was performed.

The methacrylic resin composition within the scope of the claims, even when the kind and amount of the additive and the copolymerization component of the base resin are changed, as shown in Table 1, the generation of mold cloud and mold release It was confirmed that resistance pressure was reduced and surface properties were greatly improved over the conventional products.

Similarly, Table 1 shows the results of comparative examples when the purity of the additive is low or the composition is different. In these cases, the number of mold clouding occurrences and injections is small, the release resistance pressure is high, or the additive remains on the surface of the molded product, causing delamination,
In addition, the adhesion of the vapor-deposited film is deteriorated, and the yield is lowered in the secondary process such as surface treatment, so that the moldability, releasability, and surface property are very poor as compared with the examples. Was there.

Example 8 75 Sodium polymethacrylate aqueous solution 150 g, disodium hydrogen phosphate 100 g as a suspension stabilizer in a pressure resistant reaction tank,
32.4 kg of deionized water with 3 g of sodium dihydrogen phosphate dissolved
MMA21.17kg, MA0.43kg, azobisisobutyronitrile
22 g, octyl mercaptan 43 g, additive A 43 g and additive G 5 g were added, and after thorough mixing and stirring, the mixture was heated to 80 ° C. After the exothermic peak, heat polymerization was carried out at 120 ° C. for 60 minutes. After the obtained beads were pelletized with an extruder having a cylinder diameter of 40 mm, the same evaluation as in Example 1 was carried out. As a result, the mold cloud was not generated at 100 injections at all, and the mold release resistance pressure was 20 kg / cm. No. ² was good releasability. The appearance of the surface of the molded product was good, and the adhesion of the MgF ₂ vapor-deposited film was good without peeling.

(Effects of the Invention) As described above, the present invention provides a methacrylic resin having an intrinsic viscosity of 0.30 to 1.0 (dl / gr) in chloroform at 20 ° C.
Represented by 80-99% by weight of a fatty acid mixture (I) containing 80% by weight or more of saturated fatty acid having 20-25 carbon atoms, 100 parts by weight of glyceride stearate, glyceride behenate and the above general formula (A) A methacrylic resin composition for injection molding, which comprises 0.01 to 0.5 part by weight of an aliphatic mixture consisting of 1 to 20% by weight of at least one kind of fatty acid ester (II) consisting of a compound. The mold release of the molded product is good at the time of mold release, and the occurrence of cloud stains on the surface of the mold and the molded product is suppressed, so there are few molding problems and the operating rate and productivity are significantly improved. It has the advantage that it can be produced in high yield without the occurrence of problems in secondary processing such as vapor deposition, and is suitable as a base material for plastic lenses, prisms, video disks, information recording media and the like.

Further, since the amount of the fatty acid mixture added is small, the moldability can be improved without impairing the excellent transparency and heat resistance, which are the characteristics of the methacrylic resin, and it is excellent as an injection molding material.

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Claims (2)

[Claims] (1) An intrinsic viscosity at 20 ° C. in chloroform of 0.30 to 1.
80-99% by weight of a fatty acid mixture (I) containing 80% by weight or more of a saturated fatty acid having 20-25 carbon atoms, 100% by weight of a methacrylic resin of 0 (dl / gr), glyceride stearate, and behenic acid Glyceride and general formula (A) R ₁ COOR ₂ (A) [wherein, when R ₁ is C _n H _{2n + 1} , R ₂ is C _{n + I} H _{2n + 3} (n is 13 to 21).
Represents an integer. ), Or R ₁ is C ₁₇ H ₃₅ , R ₂ is C
H ₃ and C ₄ H ₉ . ] 1 to 20% by weight of at least one fatty acid ester (II) consisting of a compound represented by
A methacrylic resin composition for injection molding, which comprises 01 to 0.5 part by weight. 2. The methacrylic resin composition for injection molding according to claim 1, wherein the fatty acid mixture (I) contains 80% by weight or more of a saturated fatty acid having 22 carbon atoms.