JPS5896641A - Styrene-methacrylic acid copolymer 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 The present invention relates to a styrene-methacrylic acid copolymer resin composition which has excellent heat resistance, oil resistance, abrasion resistance, fatigue resistance and creep resistance.

Conventionally, general-purpose polystyrene resin has been widely used as a general-purpose resin due to its high moldability, transparency, and low price. Due to the drawback that its abrasion and oil resistance are significantly inferior to other plastics, semi-engineering plastic-like performance is required for use in high-end household goods, materials for light electrical appliances, precision industrial materials, and durable consumer goods. Currently, its use is severely restricted in the field of

Styrene-acrylonitrile copolymer (As
Representative examples include styrenic copolymers such as styrene-maleic anhydride copolymer (SMA resin), styrene-butadiene-acrylonitrile copolymer (ABS resin), and the like.

However, all of the above styrene-based copolymers have the same hardness and hardness that general polystyrene resins originally had.
Polystyrene resin does not have any versatility because improvements are made at the expense of some of its characteristics, such as transparency and moldability, as well as economic efficiency and safety.

Surprisingly, the heat resistance, oil resistance, and abrasion resistance of these styrenic copolymers have not actually been improved that much, and their durability against repeated loads (fatigue resistance), Due to poor dynamic properties such as durability against static loads (creep resistance), there are still many problems when used in the above-mentioned fields.

Therefore, in order to solve these problems, attempts have been made to copolymerize styrene monomer with other copolymerizable acrylic monomers, among which copolymerization of styrene monomer and methacrylic acid monomer Coalescing is known to have properties such as excellent heat resistance, oil resistance and abrasion resistance.

However, in terms of industrial manufacturing methods and quality,
Although many drawbacks remain unresolved, as a molding material,
It has not yet been commercialized.

For example, in the production of styrene-methacrylic acid copolymer (hereinafter also referred to as "8M resin") by emulsion polymerization, an anionic or nonionic emulsifier is usually used, and potassium persulfate or ammonium persulfate is used as an initiator. However, the limitations of this method are that the emulsifier remains in the preferred copolymer and the molded product is markedly colored, and that if the amount of methacrylic acid is increased,
It was not practical due to quality defects such as the occurrence of craze when left unattended.

In addition, when attempting to obtain the 8M resin by bulk polymerization, the composition of the copolymer will be non-uniform due to the difference in the reactivity ratio of each monomer, and the molded product will be milky white and opaque. Not only is it impractical in terms of quality, but it is also unavoidable to reduce production efficiency because the reaction rate needs to be delayed in order to have a sufficiently practical molecular weight, so it is not industrially viable after all.

Furthermore, although the molded products obtained by the suspension polymerization method are relatively transparent without coloring, if the amount of methacrylic acid increases, craze will occur in the molded products when left unused, and the desired heat resistance will naturally be limited. As a result, a product with satisfactory performance could not be returned.

In addition, attempts have been made to overcome the disadvantages of opacity and generation of craze when left unused, such as lowering the molecular weight, reinforcing with rubber, and adding a third component such as methyl acrylate or ethyl acrylate, which have a low glass transition point. However, at present, it has not been possible to obtain a copolymer with excellent performance.

However, as a result of intensive research by the present inventors in order to obtain an 8M resin that eliminates all of the various drawbacks described above, the present inventors found that it is preferable to have a weight average molecular weight (MY) within a specific range, and a further specific range of 8M resin. The ratio of the molecule 1i (My) to the number average molecular weight (Mn) (My/Yjn) C. Hereinafter, this ratio will be abbreviated as "dispersity" or "dispersity (¥71./1n) J." A resin composition obtained from an 8M resin and a specific saturated fatty acid and/or an ester of the fatty acid and a dihydric alcohol retains the excellent heat resistance, oil resistance, and abrasion resistance of the conventional 8M resin. Not only that, but even if the amount of methacrylic acid monomer used increases,
The present invention was completed by discovering that a molded product can still be produced which does not cause craze when left unused and has excellent mechanical strength, especially fatigue resistance and creep resistance.

That is, in the present invention, the styrene monomer is 97 to 50% by weight.
and a styrene-methacrylic acid copolymer obtained by polymerizing methacrylic acid monomer (3 to 50% by weight)), an ester (C) of a saturated fatty acid @) and/or the fatty acid ω), and a dihydric alcohol. The present invention provides a styrene-methacrylic acid copolymer resin composition consisting of, preferably, each of the above components satisfies the following conditions. First, the above copolymer (4) has a molecular weight (Mw) of 65
~600,000, and the degree of dispersion (My/
Mn) is in the range of 15 to &5,
Next, as the saturated fatty acid (I), a fatty acid having a carbon number of 15 to 32 is used, and as the ester, the specific fatty acid (B) and a divalent fatty acid having a structure represented by the formula The resin composition is characterized by using a reaction product with alcohol.A more preferable resin composition is the copolymer (1) having a melt flow index CJI8 K-6870) of α1 to
This means that it is necessary to use something within the range of 2.511/10 minutes.

Here, the 8M resin (4) refers to a product obtained by copolymerizing 97 to 50 weight of styrene monomer and 6 to 50 weight of methacrylic acid monomer, but in particular,
Molecular weight (My) and dispersity Ujv/Mn as described above
In order to obtain the 8M resin, ditertiary butyl peroxyhexahydrorthophthalate, ditertiary butyl peroxyhexahydroin heptatalate, ditertiary butyl peroxyhexahydroterephthalate, peroxyazelaic acid, etc. Difunctional alkyl peroxides such as ditertiary butyl or ditertiary butyl peroxytrimethyladipate; 1,1-ditertiary butylperoxy-
5,S,5-trimethylcyclohexane or 1,1
- organic peroxides such as difunctional peroxyketals such as ditertiary butyl peroxycyclohexane; or low temperature active organic or inorganic peroxides such as potassium persulfate or ammonium persulfate; At least one of these is used, or in addition to these, 2,2-bis(4,4'-ditertiary butylperoxycyclohexyl)propane, ditertiary butyl peroxyisophthalate, 1,1-di(tertiary butyl)propane, butylperoxy)decane, 1. -6- or 1,4-di(tert-butylperoxyisopropyl)benzene; or tert-butyl perbenzoate, dicumyl peroxide, di-tert-butyl peracetate, di-tert-butyl peroxysuccinate, or Some substances, such as ditertiary butyl peroxide, have a half-life of 10 hours.
It is preferable to use a combination system with an organic peroxide that is active at a temperature of 00° C. or higher.

The timing of adding such a radical polymerization initiator is to start the polymerization using the above-mentioned low-temperature-activated organic, non-peroxide, or low-temperature-activated peroxide before starting the polymerization, and then to increase the polymerization rate of the copolymer. It is preferable to add a high-temperature activated peroxide at any time until the polymerization rate reaches 80%. The active peroxide contains 101 to 15 parts by weight, preferably a,0
5 to 15 parts by weight. On the other hand, when using a high temperature activated peroxide, when the amount of low temperature activated peroxide used is 100 parts by weight, this high temperature activated peroxide The amount used is 5 to 100 parts by weight, preferably 10 to 100 parts by weight.
A range of 50 parts by weight is suitable.

The combined use of such high-temperature-activated organic peroxides can be said to be an effective means because it can shorten the reaction time and reduce the amount of monomer remaining in the product.

The component 8M resin (4) constituting the composition of the present invention uses only the above-mentioned low-temperature active type peroxides, or uses a mixed system of these and high-temperature active type peroxides, It can be prepared by a method commonly used for producing general polystyrene resins, particularly by a known and commonly used suspension polymerization method.

In this way, various known and commonly used polymerization methods can be applied as they are to obtain the 8M resin (4) component, but the suspension polymerization method, which is the most preferred method in the present invention, will be described below in detail. Explain.

The polymerization temperature during suspension polymerization must be set to a temperature that corresponds to the decomposition temperature of the polymerization initiator used, but usually the first stage is where the polymerization rate of the copolymer is 60 to 90%. In this case, a suitable temperature is 50 to 130°C, preferably 80 to 100°C, and then 80 to 150°C in the second stage until the polymerization is completed.
The temperature is preferably raised to 100 to 140°C.

During suspension polymerization, various surfactants such as polyvinyl alcohol, polyalkylene oxide, carboxylmethyl cellulose, hydroxyethyl cellulose, methyl cellulose, sodium polyacrylate, or sodium dodecybenzenesulfonate are usually used as suspending agents. It can be used for dehydration, washing, and after polymerization is completed.
Next, drying is carried out and the desired 8M resin is taken out.

Although the method for obtaining the 8M resin (g) having the above-mentioned molecular weight (My) and dispersity (My/Mn) is not limited to the reaction method and reaction conditions as outlined above, Copolymer resins that fall outside of these specific weight average molecular weight ranges and specific dispersity ranges may cause severe crazes and decrease in mechanical strength when left unused. The resin composition does not withstand water and is easily damaged.

The 8M resin (4) thus obtained is treated with saturated fatty acids (saturated fatty acids) and/or esters (C
) to obtain the composition of the present invention, but the timing of addition of the @) component and/or (C) component may be any time from the polymerization step of the 8M resin (4) to the melting step/pellet step. If the 8M resin is added to the melted and pelletized resin before it is melted or pelletized, or if it is press-fitted into the resin during pelletization, the heating during these steps may ,
Since a decrease in the physical properties of the 8M resin is also observed, it is particularly preferable from the viewpoint of preventing such a situation.

The obtained 8M resin (g) is then melted and pelletized, but such operations can be carried out using a conventional extrusion pelletizer.

Here, representative examples of the above-mentioned saturated fatty acids ω) constituting the composition of the present invention include palmitic acid,
C4-C fatty acids such as heptadecanoic acid, stearic acid, aragic acid, behenic acid or montan wax acid are used. It is an esterification reaction product of a dihydric alcohol such as ethylene glycol or 1,3-butanediol as shown above, and a saturated fatty acid ω) as described above, and is a product of the esterification of such a fatty acid ω) and/or mostyl (C ) was added in the amount of the obtained 8
With respect to M resin (4), Q is 01 weight or more, preferably Q is 05 weight or more. However, even if a large amount of surplus is added, there is no noticeable improvement in the physical properties of the resin composition, and it is possible that odor or bleeding may occur when the molded product is actually obtained. From the point of view of avoiding danger, it can be said that up to 0.5 weight is already sufficient.

There is no problem in adding various additives to the composition of the present invention thus obtained, as necessary.
Additives that can be used from the time of polymerization to the time of use as a molding material include plasticizers, internal lubricants, flame retardants, fillers,
Those normally used for styrenic resins, such as blowing agents or coloring agents, can be used as well.

Further, the composition of the present invention can be easily molded using a normal molding machine, but the melting temperature range of the steam is 180 to 600°C.
The best resin performance is exhibited when the temperature is preferably 220 to 280°C. If this temperature range is less than 180°C, it will be difficult to produce a satisfactory molded product, and even if the desired molded product is produced, the residual strain inherent in the molded product will be large and sufficient performance will not be exhibited. Not good. On the contrary, v30
If the temperature exceeds 0°C, poor appearance of the molded product such as sink marks, discoloration, or jetting marks may occur, and molecular breakage due to heat and shear force may occur, so sufficient performance may still be required. is demonstrated and is outstanding.

By the way, as an example of how the composition of the present invention eliminates the generation of craze upon standing and also maintains various excellent physical properties compared to copolymers produced by conventional suspension polymerization, methacrylic Table 1 shows the relationship between the amount of acid monomer used (wt%), the degree of occurrence of craze, and various physical properties along with comparative materials. We will compare the various physical properties of the Mu-S resin and the SM-Mu resin. First, Table 1 shows that even if the composition of the present invention increases the amount of methacrylic acid to 8% by weight or more, no craze occurs when left unused. It is known that the 742 Table 1 has excellent heat resistance, oil resistance, and abrasion resistance, and also exhibits characteristic effects in fatigue resistance and creep resistance. The composition of the present invention significantly improves the heat resistance, moldability, and durability required for λS resin, and also improves the oil resistance, abrasion resistance, durability, and impact performance required for 8MA resin. It can be seen that the strength has been significantly improved.

In addition to these, 8M melted and pelletized after polymerization
When the resin (4) is used, the composition of the present invention has a melt flow index (JIS 1c-68
70) is in the high molecular weight range of 0.1 to 2.5 g/10 min, but it also has the advantage that this molecular weight is maintained stably without being substantially reduced by heating during the molding process.

In addition, it goes without saying that the composition of the present invention can be obtained using the same manufacturing time, manufacturing process, and other manufacturing conditions as those of conventional polymerization methods for styrenic resins, but surprisingly, for example, the composition of the present invention The composition is a super heat-resistant resin among this type of styrene copolymer resin.
It has heat resistance that is unmatched compared to MA resin, and also exhibits better performance in terms of oil resistance, abrasion resistance, fatigue resistance, creep resistance, and impact strength, which are the drawbacks of 8MA resin. Moreover, it also has excellent practical strength and heat resistance, which is far higher than As resin, which has been widely used as semi-engineering plastics up until now. At the same time as it has heat resistance, it also has excellent moldability, fatigue resistance, and creep resistance that other As resins do not have, and it uses methacrylic acid monomer as a raw material, which is less toxic than acrylonitrile. Because of its location, it can be said that it is meaningful in terms of manufacturing, handling, and using safe and high-quality products.

As described above, the composition of the present invention is a unique product that is further upgraded compared to conventional heat-resistant styrene resins, and has a wide range of uses, such as various nameplates, cassette tapes, and cases. , fan blades, precision industrial gears, dust covers, and heat-resistant materials for miscellaneous goods.

Next, the present invention will be specifically explained with reference to Examples and Comparative Examples, and the evaluation of the physical property test of the resin was carried out in accordance with the following procedure.

In addition, "fluidity" is adopted as a measure of moldability,
For this purpose, we have shown the data on the Melt Flow Index.

■ Melt flow index Compliant with JIS K-6870.

The molecular weight (MY) is determined by the light scattering method; on the other hand, the molecular weight (M
n) was obtained by the osmotic pressure method, and the degree of dispersion was calculated from both of these molecular sacs.

■Tensile strength Compliant with ASTM K-6871.

■Bending strength Based on ASTM D-790.

■Bicat softening point Compliant with ASTM K-7206.

■Copper silver hardness test Compliant with JIS K-5400.

■ Occurrence of unattended craze In accordance with ASTM K-6871, a 1-ounce injection molding machine (in-line screw type [SA
After storing the test piece molded by Y-501tJ in a thermostatic chamber (25° C.) for one week, the occurrence of craze is observed. Since unattended looseness occurs within a week,
No more testing companies are needed.

○: No occurrence of craze was observed.

×: Occurrence of crazes was observed.

■ Indentation fracture energy According to ASTM D-790, an injection molded test piece is pushed under the following conditions: span distance 10.2+w; bending speed 50M/min; and measurement temperature 26±1°C. The deflection rate-curvature is shown by drawing a stress curve on an autograph and multiplying the cutout weight of this figure by 100. Such a test method clearly represents the durability performance of a product under load, and is simple and effective as a practical test.

■Dumbells compliant with oil resistance ASTM K-+5871 1K
Flex the dumbbell so that it has a repulsive force of F, and apply perm quick oil or salad oil to the surface of the dumbbell.
Judgment is made based on the presence or absence of cracks.

O: No cracks were observed.

△: Slight cracks occurred.

X: Significant cracks occurred.

@ Fatigue resistance characteristics Based on the ASTM D-, 671-B method, a constant plane bending fatigue method with so-called load is adopted. The measurement conditions are 150
A vibration bending stress d of 0 times/min was performed at a vibration bending stress of 55~, and the number of vibrations until the test piece broke was used as a measure of fatigue resistance. (Test temperature -25±1℃)
A radio cabinet (W200, width 120m, depth 20m, thickness 2.0m) was made by J injection molding machine at 240'
C, and use this as a test sample.The tip of the test sample has a hemispherical shape with a radius of 20 m, and a load of 50 g of its own weight is dropped on the bottom of the test sample.
The fracture height of 50 inches was determined. The test temperature was 23±1°C, and the test sample was fixed.

Example 1 51 stainless steel reaction “J” equipped with fi-hin type stirring blade
After adding distilled water 200011d to S and dissolving partially saponified polyvinyl alcohol 10J' and sodium dodecylbenzenesulfonate α059 as a suspension stabilizer,
Styrene 95ON, methacrylic acid 5011, peroxyhexahedone c1y'', ditertiary butyl 7talate 211, and tertiary butyl perbenzoate 1jl were charged in sequence. After purging the inside of the vessel with nitrogen gas, the mixture was heated under stirring at 500 rpm. Warm, 90
Suspension polymerization was carried out at 120°C for 10 hours, and the reaction was further carried out at 120°C for 6 hours. The produced granular styrene-methacrylic acid copolymer resin was washed, dehydrated, and dried. The melt flow index of the obtained copolymer resin was α5.

Next, valmitic acid Q, 1°/- (based on the weight of the resin) was added to this resin, and the cylinder was heated to a temperature of 2°C in a nitrogen stream.
It was pelletized using an extruder at 60°C. The copolymer resin composition thus obtained was injection molded at a melting temperature of 260°C, and the molded articles obtained were used for various physical property tests. The test results are shown in Tables 1 and 2.

Example 2 Example 1 except that in the suspension polymerization recipe, styrene was changed to 920j' and methacrylic acid was changed to 801.
The same procedure as above was repeated to obtain a resin composition, and a molded article was obtained in the same manner, which was used for testing.

The test results are shown in Tables 1 and 2, respectively.

Example 3 Styrene at 850I and methacrylic acid at 15ON
A resin composition was obtained in the same manner as in Example 1, except that palmitic acid was changed to 1,3-butanediol ester of montan wax acid in the same amount, and a molded article was obtained. Provided for testing. Those test results are the first
and shown in Table 2.

Example 4 A reactor similar to Example 1 was charged with 200% of distilled water, and 1% of carboxymethyl cellulose was added as a suspension stabilizer.
09, Sodium dodecylbenzenesulfonate Q, O
! After M was dissolved, 800Ii of styrene, 200L of methacrylic acid, 41 liters of ditertiary butyl peroxyhexahydroterephthalate, and 11 tertiary butyl perbenzoate 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 7 hours, and then at 120°C.
The reaction was carried out at ℃ for 3 hours. The melt flow index of the produced granular styrene-methacrylic acid copolymer resin is 0.
It was 1.

This resin contains cerotic acid α2- and stearic acid I:L.
2% (each based on the resin weight) was added and pelletized in an extruder with a cylinder temperature of 260° C. in a nitrogen stream.

The copolymer resin composition thus obtained was injection molded at a melting temperature of 260° C., and the molded articles obtained were used for various tests. The test results are shown in Tables 1 and 2.

Comparative Example 1 2,001 liters of distilled water was charged into the same reactor as in Example 1, and carboxymethyl cellulose 10I and sodium dodecylbenzenesulfonate α were added as suspension stabilizers.
After dissolving 051, 920 Jl of styrene, 80 I of methacrylic acid, lauroyl peroxide II, and 111 tert-butyl perbenzoate were charged in sequence. After purging the inside of the vessel with nitrogen gas, the mixture was stirred at 500 rpm. The temperature was raised to 80°C, suspension polymerization was carried out at the same temperature for 9 hours, and further 1
The reaction was continued at 17° C. for 4 hours, and the melt flow index of the resulting granular styrene-methacrylic acid copolymer resin was 0.

Next, this resin was heated to a cylinder temperature of 26°C in a nitrogen stream.
It was pelletized using an extruder at 0°C. The resin composition thus obtained was injection molded at a melting temperature of 230°C,
The molded article obtained here was used for testing. The test results are shown in Tables 1 and 2.

Comparative Example 2 A resin composition was obtained by repeating the same operation as in Comparative Example 1, except that α2-behenic acid (based on the resin weight) was added to the obtained copolymer resin, and a molded article was obtained. The molded product thus obtained was used for testing. The test results are shown in Tables 1 and 2.

Comparative Example 3 Distilled water 200011j was charged in the same reactor as in Example 1, and partially saponified polyvinyl alcohol 10I and sodium dodecylbenzenesulfonate n, os II were dissolved as suspension stabilizers, and then styrene 85[
[', methacrylic acid j501, benzoyl peroxide 611
and tert-butyl perbenzoate 11 were sequentially charged. After replacing the inside of the vessel with nitrogen gas, 50. The temperature was raised under stirring using an Orpm, and suspension polymerization was carried out at 80° C. for 9 hours. The melt 70-index of the produced granular styrene-methacrylic acid copolymer resin was t5.

Next, cerotic acid α2s and stearic acid 0.256 (each based on the weight of the resin) were added to this resin, and the resin was pelletized in an extruder with a cylinder temperature of 260° C. in a nitrogen stream. The copolymer resin composition thus obtained was injection molded at a melting temperature of 260° C., and the molded product thus obtained was used for testing. The test results are shown in Tables 1 and 2.

Claims (1)

[Scope of Claims] t Styrene obtained by polymerizing 97 to 50 weight of styrene monomer and 6 to 50 weight of methacrylic acid monomer
methacrylic acid copolymer), saturated fatty acid ω) and/
or an ester (C) of the fatty acid and a dihydric alcohol;
A styrene-methacrylic acid copolymer resin composition comprising: Styrene-methacrylic acid copolymer (A) marked with z wM
At, has a weight average molecular weight (My) of 350,000 to 600,000, and has a ratio (W1w/in) of weight average molecular weight (My) to number average molecular weight (Mn) K of 15 to '5.5. 2. The composition according to claim 1, wherein the composition is of a composition comprising: 5. The composition according to claim 1, wherein the above-mentioned saturated fatty acid @Sukehiro has a carbon number of 15 to 32. 4. The ester (C) described above is a reaction product of a saturated fatty acid having a carbon number of 15 to 32 and a dihydric alcohol having a structure represented by the formula % (1) A composition according to claim 1.