JPH04236256A - Methacryl resin composition - Google Patents

Abstract

PURPOSE:To improve mold release properties of a methacryl resin by mixing a specified hydrocarbon mixture. CONSTITUTION:With 100 pts.wt. methacryl resin, 0.01-0.5 pts.wt. hydrocarbon mixture containing >=70wt.% 20-26C saturated chain material excellent in heat resistance can be obtained without damage to the excellent optical properties essential to a methacryl resin.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a methacrylic resin that exhibits good releasability from a mold during injection molding.

0002

[Prior Art] Methacrylic resin is used in many fields, including optical elements such as lighting, signboards, vehicles, optical video discs, and lenses, due to its excellent transparency and weather resistance. When used as a molding material, complex molds or molds with high dimensional accuracy are easily affected by the volatile content of the resin, resulting in poor mold release and cloudiness on the surface of the molded product. had.

To prevent these problems, methacrylic resin molding materials usually contain 0.05 to 1.0 parts by weight of a lubricant such as higher alcohols or higher fatty acid esters.

0004

[Problems to be Solved by the Invention] However, the method of adding a mold release agent described above does not have sufficient effect, and the added lubricant may cause stains or clouds on the surface of the mold or molded product. However, due to the lack of mold release performance, there were problems such as mold release failure in which the injection molded resin remained on the mold surface.

[0005]

[Means for Solving the Problems] In view of the current situation, the present inventors have made extensive studies to provide a methacrylic resin with good mold release properties that does not have the above-mentioned problems, and have developed the present invention. reached.

That is, the present invention uses 0.01 to 0.0% of a hydrocarbon mixture containing 70% by weight or more of a saturated chain hydrocarbon having a melting point of 65° C. or less and having 20 to 26 carbon atoms per 100 parts by weight of a methacrylic resin. This is a methacrylic resin composition containing 5 parts by weight.

The methacrylic resin of the present invention refers to a methyl methacrylate homopolymer or a copolymer obtained by polymerizing a mixture of methyl methacrylate and other copolymerizable monomers having vinyl groups.

Examples of copolymerizable monomers include acrylics such as methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, butyl acrylate, cyclohexyl acrylate, phenyl acrylate, benzyl acrylate, and 2,2,2-trifluoroethyl acrylate. Acid esters, methacrylic acid esters such as ethyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, and 2,2,2-trifluoroethyl methacrylate, vinyl compounds such as acrylonitrile and styrene, and acid anhydrides such as maleic anhydride and itaconic anhydride. , cyclohexylmaleimide,
Examples include maleimide compounds such as phenylmaleimide. The method for producing the methacrylic resin of the present invention is not particularly limited, and it can be produced by existing polymerization methods such as suspension polymerization and bulk polymerization.

Next, the hydrocarbon mixture containing 70% by weight or more of a saturated chain hydrocarbon having a melting point of 65° C. or less and a carbon number of 20 to 26 used in the present invention includes icosane, heniicosane, docosane, tetracosane, A saturated chain hydrocarbon mixture containing 70% by weight or more of pentacosane or hexacosane and may also contain other hydrocarbons.

[0010] Saturated chain hydrocarbons having less than 20 carbon atoms have too high volatility and cannot exhibit sufficient performance as a mold release agent. On the other hand, saturated chain hydrocarbons having more than 26 carbon atoms have poor compatibility with methacrylic resins and cause mold stains and cloudy molded products.

In addition, if the melting point exceeds 65°C, taking into account the mold temperature in ordinary injection molding of methacrylic resin, the mold release agent will precipitate on the mold surface, resulting in defects on the surface of the molded product. Become.

The content of the above saturated hydrocarbon mixture is:
0.01 to 0.0% per 100 parts by weight of methacrylic resin.
5 parts by weight. Addition amount of saturated hydrocarbon mixture is 0.0
If it is less than 1% by weight, its performance as a mold release agent will not be fully exhibited and it will likely cause peeling or cracking of the molded product. On the other hand, if the amount added exceeds 0.5 part by weight, the saturated chain hydrocarbon mixture will excessively adhere to the mold, causing stains on the surface of the mold and cloudiness on the surface of the molded product.

[0013] The saturated chain hydrocarbon mixture can be added by dissolving it in the monomer before polymerization and polymerizing it by an existing polymerization method, or by extruding and shaping the polymer obtained by an existing polymerization method. Any method such as a method of adding at the same time may be used.

In the methacrylic resin composition of the present invention, a hydrocarbon mixture can be used with a lubricant such as higher alcohols or higher fatty acid esters as a mold release agent. Additionally, additives such as ultraviolet absorbers, heat stabilizers, and colorants may be mixed in and used as required.

[0015]

[Examples] The present invention will be specifically explained below with reference to Examples. Note that "%" and "parts" in the examples indicate "% by weight" and "parts by weight", respectively. In addition, the mold releasability was evaluated by the following method. The mold for examining mold releasability shown in Fig. 1 was made into a FAN.
It was set in a UC injection molding machine MODEL 100A, a pressure sensor was attached to the ejecting pin of the mold, the signal was converted into an electrical signal proportional to the sensor through an amplifier, and the signal was converted into a pressure unit using a recorder and recorded. To eliminate the influence between each material, the mold was cleaned with acetone when changing materials. The pressure sensor used was a crystal piezoelectric insertion type cavity internal pressure sensor 9221 manufactured by Kistler.
The model and amplifier are Kistler charge amplifier type 5007.
The recorder is YOKOGAWA MODEL 3655
E ANALYZING DECORDER was used. The injection molding conditions were the following two types.

■Type A Mold setting temperature 65°C Heating cylinder setting temperature 250°C Injection pressure 300, 340, 380kg
/cm2 Injection time 10 seconds ■Type B Mold setting temperature 63℃ Heating cylinder setting temperature 265℃ Injection pressure 360, 390, 420kg
/cm2 injection time 10 seconds

Example 1 91.5 parts by weight of methyl methacrylate (MMA), 8.5 parts by weight of methyl acrylate (MA), 0.35 parts by weight of n-octyl mercaptan, and 0.002 parts by weight of di-tert-butyl peroxide. A monomer mixture consisting of 15 parts of
The mixture was continuously supplied to a reaction tank having an internal volume of 300 ml. The reaction tank was filled with nitrogen, the internal pressure was adjusted to 8 kg/cm2 gauge pressure, and the polymerization temperature was adjusted to 155°C. After about 8 hours,
The feed rate was set to 25/hr and the operation was shifted to continuous operation. Note that the stirring rotation speed was 90 rpm, and the residence time was 4.7 hours.

[0018] The reaction product was separated by a volatile matter separation device consisting of a twin-screw vent extruder (screw: 900 mmφ x 12
00 mm, vent length: 600 mm), and was degassed and pelletized at a cylinder temperature of 230°C, a die temperature of 225°C, and a vent part vacuum degree of 10 mmHg abs or less. At this time, additive A (a saturated chain hydrocarbon mixture containing 84.2% by weight of saturated chain hydrocarbons having 20 to 26 carbon atoms; trade name: Paraffin Wax 115 Nippon Wax) is added to the additive injection system (21 in Figure 2). 0.05 part of
Additive D (containing 85% by weight or more of styryl alcohol:
0.15 part of Calcol 86 (trade name, manufactured by Kao Corporation) was added.

Example 2 For 99.4 parts by weight of MMA and 0.6 parts by weight of MA, n-
0.24 parts by weight of octyl mercaptan,
A monomer mixture containing 0.002 parts by weight of butyl peroxide was polymerized in the same manner as in Example 1. However, the polymerization temperature was 160°C, the residence time was 4.1 hours, the cylinder temperature of the vent extruder was 260°C, and the die temperature was 235°C. In addition, 0.05 parts by weight of additive A from the additive injection system,
Additive C was added in an amount of 0.05 parts by weight.

Example 3 The additive added from the additive injection system was
Example 1 except that parts by weight and additive D were 0.15 parts by weight.
The experiment was conducted in exactly the same way.

Example 4 The additive added from the additive injection system was added to Additive B0.05.
Example 2 except that parts by weight and additive C were 0.05 parts by weight.
The experiment was conducted in exactly the same way.

Comparative Example 1 The additive added from the additive injection system was
An experiment was conducted in exactly the same manner as in Example 1 except that parts by weight were used.

Comparative Example 2 An experiment was conducted in exactly the same manner as in Example 2, except that the additive added from the additive injection system was 0.1 parts by weight of additive C.

Table 1 shows the conditions of each example and comparative example and the type of injection conditions used to evaluate mold releasability.

[0025]

[Table 1]

[0026] The melt flow rate, which is an index of the molding fluidity of the pellets obtained in Examples 1 and 3 and Comparative Example 1, is a value measured at a load of 3.8 kg based on ASTM-D1238, and is 18 to 20 g. /10 minutes,
It can be said that the molding fluidity is equivalent. In addition, Examples 2 and 4
The melt flow rate, which is an index of the molding fluidity of the pellets obtained in Comparative Example 2, is a value measured at a load of 10 kg based on ASTM-D1238, and is 8 to 10 g/10.
It can be said that the molding fluidity is equivalent.

FIG. 3 shows evaluation of mold releasability when the pellets obtained in Examples 1 and 3 and Comparative Example 1 were injection molded, that is, the relationship between injection pressure and ejection force. The larger the ejection force, the greater the force required to release it from the mold.
It can be said that the mold releasability is poor. As shown in FIG. 3, when compared with Comparative Example 1, Examples 1 and 3 require a lower ejection force, and the release property is better when the saturated chain hydrocarbon mixture additive is added.

Further, FIG. 4 shows the relationship between injection pressure and ejection force when injection molding was performed using the pellets obtained in Examples 2 and 4 and Comparative Example 2. Similar to Fig. 3, it can be said that the larger the ejection force is, the worse the mold release property is, but in Examples 2 and 4, when compared with Comparative Example 2, the ejection force was lower, and the hydrocarbons of the saturated chain hydrocarbon mixture were It can be said that the mold release property is better when added.

[0029]

[Effects of the Invention] The methacrylic resin for optical information recording media of the present invention is a molding material with excellent heat resistance, good fluidity, and productivity while retaining the excellent optical properties inherent to methacrylic resin. Because it can be suitably used as
It has excellent industrial effects.

[Brief explanation of the drawing]

FIG. 1: HD of the methacrylic resin of the present invention and the conventional copolymer of methyl methacrylate and ethyl acrylate.
It shows the relationship between T and MRF.

FIG. 2 is a polymerization apparatus used in Examples.

[Explanation of symbols]

1 Storage tank 2, 4, 7, 13, 15 lines 3,14 Pump 6 Heat exchanger 8 Reaction tank 9 Spiral ribbon type stirrer 10 Jacket 11,12 Opening 16 Volatile separator 18 Screw 19 Vent 20 Means for heating or cooling 21 Additive injection system

FIG. 3 shows the relationship between injection pressure and ejection force when injection molding was performed using pellets obtained in Examples 1 and 3 and Comparative Example 1.

FIG. 4 shows the relationship between injection pressure and ejection force when injection molding was performed using pellets obtained in Examples 2 and 4 and Comparative Example 2.

Claims (1)

[Claims] 1. A hydrocarbon mixture containing 70% by weight or more of a saturated chain hydrocarbon having a melting point of 65° C. or lower and having 20 to 26 carbon atoms, based on 100 parts by weight of methacrylic resin.
A methacrylic resin composition containing 0.5 parts by weight.