JPS581142B2 - Styrenic resin composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a styrenic resin composition that has excellent mechanical strength, particularly fatigue resistance and creep resistance.

Conventionally, general-purpose polystyrene resin has been widely known and used as a general-purpose resin due to its advanced molding performance, transparency, and low price.However, on the other hand, the impact strength and fatigue resistance of injection molded products are poor. Because it has the disadvantage of being significantly inferior to other plastics, its use is severely restricted in fields that require durable strength, such as high-end household goods, durable consumer goods, industrial materials, and industrial materials. is the current situation.

Examples of resins that improve the drawbacks of general polystyrene resins include styrene-butadiene copolymer (HIP).
Styrenic copolymers such as S), styrene-acrylonitrile copolymer (AS resin), and styrene-butadiene-acrylonitrile copolymer (ABS resin) are known as representative examples.

However, in order to improve the strength of such copolymers, some of the inherent characteristics of general-use polystyrene resins such as hardness, transparency, moldability, and economic efficiency are sacrificed. cannot have the versatility of

Surprisingly, this type of styrene-based copolymer has dynamic properties such as durability against repeated loads (fatigue resistance) and durability against static loads (creep resistance) that are superior to those of general-use polystyrene. They are not much improved compared to resins and still have many problems in their use in the fields mentioned above.

In order to solve these problems, attempts have been made to increase the molecular weight of styrenic resins, but many drawbacks in terms of manufacturing, safety and hygiene, quality, etc. remain unresolved.

For example, styrenic resins are generally produced by suspension polymerization using benzyl peroxide and tertiary butyl perbenzoate, or benzyl peroxide and tertiary butyl peracetate as described in Japanese Patent Publication No. 29-5644. It is produced using a combination of polymerization initiators, but if you try to increase the molecular weight with such a polymerization initiator, it is necessary to lower the initiator concentration, which takes a long time for the reaction and reduces production efficiency. Not only that, the obtained polymer has a considerable amount of unreacted monomer remaining, which poses health and safety problems, and it also has quality defects such as the heat resistance of molded products, foaming during molding, and the occurrence of silver streaks. It was not practical because of the

In addition, when using ditertiary butyl peroxyisophthalate, ditertiary butyl peroxysuccinate, ditertiary butyl peroxyphthalate, etc., which are high temperature active difunctional organic peroxides, It is necessary to carry out the reaction at a high temperature of 100°C or higher, but since dispersion in the suspension polymerization system becomes unstable at such high temperatures, dispersion is carried out to prevent agglomeration due to agglomeration of dispersed particles during polymerization. It is necessary to take measures such as adding a large amount of stabilizer.

Moreover, the polymer obtained by this method has a wide particle size distribution, which causes manufacturing problems such as dehydration, drying, and drainage, and furthermore, the polymer may lack transparency or a large amount of unreacted monomer may be contained in the product. There were problems such as the presence of residual particles, and it was not possible to obtain a product with satisfactory performance.

The present inventors conducted various studies to obtain a styrenic resin that solved the above-mentioned drawbacks, and found that a certain type of low-temperature-activated difunctional organic peroxide was used as an initiator during polymerization. A resin composition obtained from a styrenic resin obtained by polymerizing a polymer in combination with a functional organic peroxide, which is further melted and granulated in a nitrogen stream, and a certain type of acid has excellent mechanical strength, especially fatigue resistance. The present inventors have discovered that this material exhibits excellent effects on properties and creep resistance, and have completed the present invention.

That is, the present invention uses a composition consisting of a styrenic monomer alone or, if necessary, another vinyl monomer copolymerizable with the monomer and/or a rubbery substance, as a radical polymerization initiator ( 1) at least one of ditertiary butyl beroxyhexahydrophthalate, ditertiary butyl bereoxyhexahydroisophthalate, and ditertiary butyl bereoxyhexahydroterephthalate; and (2) high temperature activity. The present invention relates to a styrenic resin composition consisting of a styrene resin (A) and behenic acid (B) obtained by polymerizing using a type organic peroxide, followed by melting and granulation in a nitrogen stream. .

The styrenic resin of the present invention obtained by melting and granulating after polymerization has an ultra-high weight average molecular weight of 400,000 to 800,000, and this molecular weight is stable with almost no decrease even when heated during molding. It is held in

It goes without saying that the styrene resin composition of the present invention can be obtained using the same manufacturing time, manufacturing process, and manufacturing conditions as conventional styrene resins, but surprisingly, for example, the polystyrene resin composition of the present invention Among styrene resins, it exhibits far higher fatigue and creep resistance than conventional AS resins, which are said to have high strength.On the other hand, it has superior moldability and transparency compared to conventional general-use polystyrene. It is as good as resin, and even better than polystyrene resin in terms of rigidity and strength.

Furthermore, it is a high-quality product with good thermal stability and low content of unreacted monomers.

In the present invention, at least one of ditertiary butyl beroxyhexahydrophthalate, ditertiary butyl bereoxyhexahydroisophthalate, and ditertiary butyl bereoxyhexahydroterephthalate (hereinafter referred to as " The radical polymerization initiator used in combination with the "low-temperature-activated organic peroxide" is a high-temperature-activated organic peroxide, preferably a high-temperature-activated organic peroxide whose decomposition temperature with a half-life of 10 hours is 95°C or higher. It is an oxide.

Such high temperature active organic peroxides include 1,1-
Di-tertiary peroxy-3,3,5-trimethylcyclohexane, 2,2-bis(4,4'-di-tertiary butylperoxycyclohexyl)propane, ditertiary butyl peroxyisophthalate, peroxyphthalic acid Di-tertiary butyl, 1,10-di-(tert-butylperoxy)decane, 1,3- or 1,4-di-(tert-butylperoxyisopropyl)benzene, tertiary-butyl perbenzoate, Tertiary butyl peracetate, ditertiary butyl peroxysuccinate, dicumyl peroxide, ditertiary butyl peroxide, tertiary butyl peroxyadipate, ditertiary butyl peroxyazelaate, vinyl tris( These include tertiary butylperoxy)silane and the like.

Components constituting the styrenic resin of the present invention include styrene; styrene in which the hydrogen atom of the benzene nucleus is substituted with a halogen atom or an alkyl group (C1 to C4), for example,
Styrenic monomers such as O-chlorostyrene, P-chlorostyrene, P-methylstyrene, 2,4-dimethylstyrene, tertiary butylstyrene; and α-alkyl (C1 to C4) substituted styrene, such as α-methylstyrene In addition to one or more types of monomers, other vinyl monomers or rubber-like substances copolymerizable with the monomers may be added, if necessary.

Other vinyl monomers that can be copolymerized with styrene monomers include acrylonitrile monomers such as acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, and vinylidene cyanide; (meth)acrylic acid, (meth)
(Meth)acrylic acid and its esters such as methyl acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, and glycidyl methacrylate; vinyl acetate,
Examples include various vinyl monomers such as vinyl chloride, vinylidene chloride, vinylpyrrolidone, acrylamide, dimethylacrylamide, (anhydrous) maleic acid, (anhydrous) itaconic acid, maleimide, vinyl ketones, and vinyl ethers; The substances include conjugated 1,3-diene polymers such as butadiene, isoprene, and chloroprene;
Butadiene-styrene copolymer, butadiene-acrylonitrile copolymer, butadiene-styrene-acrylonitrile copolymer, isobutylene-acrylic acid ester copolymer, butyl rubber, ethylene-propylene terpolymer (EPDM), and the like can be used.

When copolymerizing a styrene monomer with other vinyl monomers or rubber-like substances, it is necessary that the styrene monomer constitute at least the main component of the copolymer. In addition, if a rubbery substance is used, the ratio of its use should be the total amount of styrene monomer and other vinyl monomers.
It is desirable to set it as the range of 0.5-20 weight parts to 00 weight parts.

The timing of adding the radical polymerization initiator used in the polymerization of the styrenic monomers described above is such that a low temperature activated organic peroxide and a high temperature activated organic peroxide are added before the start of polymerization, or a low temperature activated organic peroxide is added before the start of polymerization. After starting the polymerization using the peroxide, it is preferable to add the high temperature active type organic peroxide at any time until the polymerization rate of the monomer reaches 80%.

The amount of the polymerization initiator added is 0.00 parts by weight of the low temperature activated organic peroxide per 100 parts by weight of the total amount of monomers charged at the initial stage of polymerization.
01 to 1.5 parts by weight, preferably 0.05 to 0.5 parts by weight, while the high-temperature active type organic peroxide is preferably used in an amount of 5 to 100% by weight of the amount of the low-temperature active type organic peroxide used. is used in a range of 10 to 50% by weight.

The styrenic resin of the present invention can be produced by any polymerization method in which the above-mentioned (1) low-temperature activated organic peroxide and (2) high-temperature activated organic peroxide can be used as a polymerization initiator, for example. Suspension polymerization method, bulk polymerization method, bulk suspension polymerization method,
It can be manufactured by emulsion polymerization method, solution polymerization method, etc.

Regarding the suspension polymerization method, which is a common method for producing general-purpose polystyrene resin, the polymerization temperature during suspension polymerization needs to be set to a temperature that corresponds to the decomposition temperature of the polymerization initiator used. Usually, the polymerization rate of the monomer is 60~
The first stage up to 90% by weight is carried out at a temperature of 50-130°C, preferably 80-100°C, and then the second stage until completion of the polymerization is carried out at an elevated temperature of 80-150°C, preferably 100-140°C. good.

During suspension polymerization, stabilizers such as magnesium carbonate, tertiary magnesium phosphate, starch, polyvinyl alcohol, polyalkylene oxide, sodium polyacrylate, polyacrylamide, polyvinylpyrrolidone, methylcellulose, carboxymethylcellulose, hydroxyethylcellulose, and EDTA are usually used. Sodium salts, various surfactants, etc. can be used as appropriate, and after completion of polymerization, dehydration, washing, and drying are performed to take out the polymer.

When polymerizing by other polymerization methods, the production conditions may be set according to conventional methods as in the case of suspension polymerization.

In the present invention, the styrene resin obtained by polymerization is then melted and granulated in a nitrogen stream, but this operation means operation in a state where oxygen in the atmosphere is cut off. For example, nitrogen gas per 1 kg of resin is This can be carried out by melting and granulating in an extruder while continuously feeding 1 liter or more.

Behenic acid may be added to the styrenic resin at any time between the melting of the styrene resin and the granulation process, or it may be added to the styrenic resin after granulation. It is particularly preferable to add it before melting or granulating it, or to press it into the resin during granulation, since this can also prevent the physical properties of the styrenic resin from deteriorating due to heating during melting or granulation.

The amount of behenic acid added is based on the styrene resin obtained by polymerization (approximately corresponds to the total amount of monomers involved in polymerization).
It is 0.01% or more, preferably 0.05% or more, and even if it is added in too large a amount, there will be no significant improvement in the physical properties of the styrene resin composition, and when actually molded products are obtained, odor, bleeding, etc. 0.5% is sufficient if safety and health considerations are taken into consideration.

Various additives may be added to the styrenic resin composition of the present invention as necessary.

Examples of additives that can be used from the time of polymerization to the time of use as a molding material include molecular weight regulators, plasticizers, and internal lubricants (
Stearic acid, etc.), modifiers (rubber-like substances, etc.), flame retardants, fillers, blowing agents, coloring agents, etc. that are commonly used for styrenic resins can also be used.

The styrenic resin composition of the present invention can be easily molded using a normal molding machine, but the melting temperature range is 180 to 3.
The best resin performance is exhibited at a temperature of 00°C, preferably 220 to 280°C.

If the melting temperature is less than 180° C., it is difficult to obtain a satisfactory molded product, and even if a desired molded product is obtained, the residual strain inherent in the molded product is large and sufficient performance cannot be exhibited.

Furthermore, if the temperature exceeds 300°C, the molded product may have poor appearance such as sink marks, discoloration, jetting marks, etc., or molecular breakage due to heat and shearing force may occur, so that sufficient performance cannot be exhibited.

The styrenic resin composition of the present invention is characterized by particularly excellent properties such as thermal stability, strength, rigidity, fatigue resistance, and creep resistance. is shown in Figure 1.

The styrene resin composition obtained in Example 1 (to be described later) (weight average molecular weight after granulation: 580,000), the commercially available general polystyrene resin "Dencastyrol MW-1" (manufactured by Denki Kagaku Kogyo Co., Ltd., weight average molecular weight 39) AST for three types of commercially available AS resin "Tyryl 783" (manufactured by Asahi Dow Industries Co., Ltd.)
Injection molded and tested according to MD-790.

(Test specimen thickness: 3 mm, width: 12.7 mm; distance between spans: 1
02mm; Bending speed 50mm/min; Measurement temperature 23±1℃
) According to FIG. 1, the polystyrene resin composition of the present invention has
It can be seen that the energy required for destruction is clearly higher than the others.

Such mechanical characteristics are universally obtained even if the test conditions and molding conditions are changed, and the same behavior is exhibited in a tensile test.

As described above, the styrenic resin composition of the present invention has superior properties such as thermal stability, strength, and rigidity, especially fatigue resistance and creep resistance, compared to conventional ones, and is also superior in moldability to conventional ones. Therefore, it is useful as a molding material.

In particular, molded products that have parts that are subjected to repeated loads or constant loads, such as containers with hinged parts and lids (cosmetic compacts, dust covers, etc.), molded products that rotate and have rotating parts (precision industrial gears, fan blades, etc.) It can be advantageously used for applications such as stirring blades for aquariums, etc.) and stacking containers (transport boxes, organizing cases, large aquariums, etc.).

Hereinafter, the present invention will be explained by giving examples, but the present invention is not limited to these examples.

In addition, evaluation of the physical property test of the resin was performed by the method shown below.

(1) 20 mg of weight average molecular weight polymer was dissolved in 12 ml of tetrahydrofuran and measured by gel permeation chromatography (GPC) at room temperature using styrene gel packing force rams of 104, 105, 106, and 107 Å.

(2) Melt flow index JIS K-6870 (200℃, 5kg load) (3)
Measure the inflow length ratio (inflow length (L)/thickness (1)) using the spiral flow.

(Injection temperature 220℃, injection pressure 830kg/cm2) (4) Bending strength ASTM D-790 (bending speed 2.5mm/min) (5)
Rockwell Hardness ASTM D-785 (M Scale) (6) Fatigue Resistance Characteristics Based on ASTM D-671-B method, so-called constant load plane bending fatigue method is adopted.

The measurement conditions were vibration bending of 1500 times/min at a vibration bending stress of 550 kg/cm2, and the number of vibrations until the test piece broke was used as a measure of fatigue resistance.

(Test temperature: 25±1°C) (7) Creep resistance properties A bending creep test was conducted on a short fence-like test piece with a thickness of 3 mm and a width of 12.7 mm under the conditions of a span distance of 102 mm and a bending stress of 34 kg in a water bath at 70°C. The deflection rate at each described time was used as a measure of creep resistance.

(8) Conical indentation strength A flat plate measuring 200 mm wide, 300 mm long, and 2 mm thick with a 1.5 mm pin gate in the center was used as the test sample, and a tip with a radius of 0. 5
A cone of 50 mm in diameter was pressed at a rate of 50 mm/min, and the maximum load at which it broke was taken as a measure of indentation strength.

(Test temperature 23 ± 1℃) (9) Falling weight failure height: A radio cabinet with a height of 200 mm, a width of 120 mm, and a depth of 20 mm was used as the test sample, and the tip was placed on the bottom with a radius of 20 mm.
Dropping a load of 50 gr on a hemispherical shape of mm, Part 5
The 0% fracture height was determined.

The test temperature was 23±1° C., and the test sample was fixed.

The measurement results are summarized in Table 1.

Example 1 2000 ml of distilled water was charged into a 5 liter stainless steel reactor equipped with a turbine-type stirring blade, and after dissolving 10 g of partially saponified polyvinyl alcohol as a suspension stabilizer and 0.05 g of sodium dodecylbenzenesulfonate, 10 g of styrene was added.
00 gr, ditertiary butyl peroxyhexahydroterephthalate 1 gr, and tertiary butyl perbenzoate 0.5 gr were sequentially charged.

After purging the inside of the vessel with nitrogen gas, the temperature was raised under stirring at 500 rpm, suspension polymerization was carried out at 90°C for 10 hours, and then reaction was carried out at 120°C for 5 hours.

The resulting granular polystyrene resin was washed, dehydrated, and dried.

The weight average molecular weight of the obtained polystyrene resin was 650,000.

0.1% (based on the resin weight) of behenic acid was added to this resin, and the mixture was granulated using an extruder with a cylinder temperature of 260° C. in a nitrogen stream.

The weight average molecular weight of the obtained pellets was 580,000.

The polymers thus obtained were injection molded at melting temperatures of 230°C and 280°C, and subjected to each measurement.

Example 2 In a 5l stainless steel reactor, 2000ml of distilled water, 10gr of tertiary calcium phosphate, 0.05gr of sodium dodecylbenzenesulfonate, 1000gr of styrene, 40gr of liquid paraffin. Charge 1 gr of di-tert-butyl peroxyhexahydrophthalate and 0.5 gr of di-tert-butyl peroxyisophthalate, and stir at 500 rpm.
Suspension polymerization was carried out at 0°C for 10 hours, then the temperature was raised to 120°C, and after reaction at that temperature for 4 hours, the produced polystyrene resin was washed, dehydrated, and dried.

The weight average molecular weight of the obtained polystyrene resin was 680,000.

0.05% of behenic acid (same as above) and 0.05% of stearic acid (same as above) were added to this resin, and granulated in an extruder with a cylinder temperature of 260° C. in a nitrogen stream.

The weight average molecular weight of the obtained granules was 600,000.

The polystyrene resin thus obtained was injection molded at melting temperatures of 220°C and 270°C, and subjected to each measurement.

Example 3 In a 5-liter stainless steel reactor, 2,000 ml of distilled water,
Tertiary calcium phosphate 10gr, sodium dodecylbenzenesulfonate 0.05gr, styrene 1,000gr
, ditertiary butyl peroxyhexahydrophthalate 1g
was charged, and suspension polymerization was carried out at 90° C. while stirring at 500 rpm.

After 5 hours of polymerization, 0.5 of 1,1-ditertiary butylperoxy-3,3,5-trimethylcyclohexane
gr was added, and the mixture was further reacted at 90°C for 5 hours.

Next, the temperature was raised to 120°C, and the reaction was completed after polymerization for 4 hours.

The weight average molecular weight of the obtained polystyrene resin was 630,000.

When 0.1% of behenic acid (same as above) was added to this resin and granulated in a nitrogen stream at a cylinder temperature of 260°C, the weight average molecular weight was 550,000.

The polystyrene resin thus obtained has a melting temperature of 2
It was injection molded at 50°C and subjected to each measurement.

Example 4 800g of ethylbenzene in a 5L stainless steel reactor
, styrene 1,200gr, liquid paraffin 48gr,
Ditertiary butyl peroxyhexahydroterephthalate 0
．． 65 gr, ditertiary butyl peroxide 0.3 gr, behenic acid 0.8 gr, and stearic acid 0.4 gr were sequentially charged.

After purging the inside of the vessel with nitrogen gas, the temperature was raised while stirring at 500 rpm, and the reaction was carried out at 90°C for 10 hours.

The temperature was then raised to 250°C, and ethylbenzene and unreacted styrene were removed under reduced pressure.

The obtained polystyrene resin was pulverized in a rotoplex and then granulated at 260° C. in a nitrogen stream.

The weight average molecular weight of the product itself was 550,000.

The resin thus obtained was injection molded at a melting temperature of 250° C. and subjected to each measurement.

Example 5 2,000 ml of distilled water was charged into a 5 liter stainless steel reactor, and after dissolving 5 gr of partially saponified polyvinyl alcohol as a suspension stabilizer, 5 gr of carboxyl methyl cellulose, and 5 gr of methyl cellulose, 600 gr of styrene,
α-methylstyrene 200g, methyl methacrylate 2
00gr, liquid paraffin 40gr, ditertiary butyl peroxyhexahydroisophthalate 1gr, and ditertiary butyl peroxide 0.5gr were sequentially charged inside the vessel, which was purged with nitrogen gas, and then heated to 90°C under stirring at 500 rpm. Suspension polymerization was carried out for 12 hours.

Next, the reaction was carried out at 115°C for 2 hours and at 130°C for 2 hours.

The weight average molecular weight of the produced granular polystyrene resin is 60
It was 10,000.

0.15% of behenic acid (same as above) was added to this resin and granulated using an extruder with a cylinder temperature of 260° C. in a nitrogen stream.

The polystyrene copolymer resin thus obtained was injection molded at melting temperatures of 240° C. and 290° C. and subjected to each measurement.

Comparative Example 1 A resin (weight average molecular weight 630,000) obtained by polymerizing with the same recipe as in Example 1 and washing, dehydrating, and drying after the polymerization was completed (weight average molecular weight 630,000) was directly used in an extruder with a cylinder temperature of 260°C. The weight average molecular weight when granulated was 380,000.

The obtained polystyrene resin was heated to a melting temperature of 220°C and 27°C.
It was injection molded at 0°C and used for each measurement.

Comparative Example 2 1,1-ditertiary butyl as a polymerization initiator for suspension polymerization
Using 1.5 gr of 3,3,5-trimethylcyclohexane and 0.59 gr of ditertiary butyl peroxide, the polymerization temperature was 1.
The recipe of Example 1 was followed except that the reaction was carried out at 00°C for 8 hours and at 130°C for 3 hours.

The weight average molecular weight of the obtained resin was 640,000.

When this was granulated as it was at 260°C, the weight average molecular weight was 390,000.

This resin was injection molded at a melting temperature of 250°C and used for each measurement.

[Brief explanation of the drawing]

FIG. 1 shows bending stress-deflection curves of the polystyrene resin composition of the present invention, a commercially available polystyrene resin for transportation, and an AS resin. The area of the shaded area indicates the energy required to destroy the polystyrene resin composition of the present invention.

Claims (1)

[Claims] 1. A composition consisting of a styrene monomer alone or, if necessary, other vinyl monomers and/or rubber-like substances copolymerizable with the monomer, as a radical polymerization initiator (1)
at least one of ditertiary butyl beroxyhexahydrophthalate, ditertiary butyl bereoxyhexahydroisophthalate, ditertiary butyl bereoxyhexahydroterephthalate, and (2) a high temperature activated organic A styrenic resin composition comprising a styrene resin (A) and behenic acid (B) obtained by polymerizing with a peroxide, followed by melting and granulation in a nitrogen stream.