JPH0384008A - Novel acrylic resin - Google Patents

Abstract

PURPOSE:To obtain the subject novel resin useful for field requiring dimensional accuracy or high speed molding because of having excellent moldability and strength by introducing a specific amount of long-chain alkyl group. CONSTITUTION:The objective resin having 5X10<4>-5X10<5> weight-average molecular weight is composed of (A) 0.01-10 pts.wt. units expressed by formula I (l)to (n) are 1-20; R<1> to R<4> are H, or 1-5C alkyl, etc.) and (B) 100 pts.wt. units comprising 50-100wt.% methyl methacrylate and 0-50wt.% ethylenic monomer (preferably methyl acrylate, etc.) copolymerizable with said methyl methacrylate. Said resin is preferably obtained by polymerizing methyl methacrylate and ethylenic monomer using polymerization initiator having >=3, preferably 5-30 units expressed by formula II.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a novel acrylic resin.

More specifically, the present invention relates to a novel acrylic resin that has excellent strength and moldability by introducing a specific amount of long-chain alkyl groups into the acrylic resin.

The acrylic resin of the present invention has a yield point and a breaking point in a bending stress strain test, and has particularly excellent fracture resistance against external stress applied to the resin when exhibiting a whitening phenomenon.

(Conventional technology and issues) Acrylic resins are used in industrial fields such as automobile parts, electrical product parts, optical materials, and signboards by taking advantage of their properties such as excellent transparency, weather resistance, high rigidity, and chemical resistance. Widely used. Recently, there has been a strong demand for improvements in the strength and moldability of acrylic resins in order to further expand the field of application and increase product productivity.

Acrylic resin, which is a hard plastic, tends to break before reaching the yield point in the -III bending strain test, and its mechanical strength is not necessarily sufficient depending on the field of use.

It has been known that increasing the average molecular weight can improve the strength of acrylic resins, but increasing the average molecular weight reduces moldability. Plasticizers have been used to compensate for the decrease in moldability, but the addition of plasticizers tends to lower heat resistance, stiffness, and strength, which cannot be addressed simply by increasing the average molecular weight.

Furthermore, a method of improving the strength by blending a rubbery polymer with an acrylic resin is also known, but this tends to impair the characteristics of the acrylic resin such as transparency and high rigidity.

(Means for Solving the Problems) In view of the current situation, the present inventors continued intensive research to improve the strength and moldability of acrylic resin at the same time. As a result, the general formula (A): (4 in the formula! , m, n are integers from 1 to 20, and R1, R
1, Rs and Ra are hydrogen, an alkyl group having 1 to 5 carbon atoms,
cyclohexyl group or phenyl group) and 0 to 100% by weight of methyl methacrylate and one or more types of ethylene monomer copolymerizable with methyl methacrylate. 50% by weight of the structural unit (I
I), and the constituent unit (1) is the constituent unit (II).
It was discovered that a new acrylic resin with a weight average molecular weight of 50,000 to 500,000 and a weight average molecular weight of 50,000 to 500,000 exhibits excellent strength and moldability, and the present invention was completed. did.

The acrylic resin of the present invention has a yield point and a breaking point in a bending stress strain test, and has particularly excellent fracture resistance against external stress applied to the resin when exhibiting a whitening phenomenon.

Although it is not necessarily clear why the acrylic resin of the present invention has excellent strength and moldability, it is possible to This is considered to be because the structural unit (1) having a long-chain alkyl group in the structure functions effectively as a soft segment.

In the present invention, the ratio of the structural unit (1) to the structural unit (If) is important, and the ratio of the structural unit (1) to the structural unit (II) is 0.01 to 10% by weight, preferably 0.05 to 10% by weight. 5
Weight%. When the content of the structural unit (■) is less than 0.01% by weight, the improvement in strength and moldability of the acrylic resin is insufficient. In addition, the structural unit (1) is 10% by weight
When it exceeds 100%, the rigidity and heat resistance of the acrylic resin tend to decrease.

In particular, when the structural unit (1) is 0.05% by weight or more,
It is preferable because it has a yield point and a breaking point in a bending stress stress test, exhibits a whitening phenomenon, and has particularly excellent fracture resistance against external stress applied to the resin.

In the present invention, in order to introduce the structural unit (I) into the acrylic resin, the general formula (B): Rz R4 (wherein j!, m, and n are integers of 1 to 20, R+,
Rz, Rs, R4 represent hydrogen, an alkyl group having 1 to 5 carbon atoms, a cyclohexyl group, or a phenyl group), preferably 5 to 30 repeating units.
Methyl methacrylate 50~
100% by weight and 0 to 50% by weight of one or more types of ethylene monomer copolymerizable with methyl methacrylate.

As such an initiator, for example, those having the following repeating units can be used.

+ C-(CHI) &-CB-(CHri?-C-0
-0 +tHS CHs CH2 In the present invention, the structural unit (II) is 50 to 100% by weight of methyl methacrylate and 0 to 1 or more types of ethylene monomer copolymerizable with methyl methacrylate.
50% by weight.

Examples of ethylene monomers copolymerizable with methyl methacrylate include acrylic acid, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, isobutyl acrylate, t-butyl acrylate, and 2-acrylate. Ethylhexyl, lauryl acrylate,
Acrylic acid or acrylic acid esters such as cyclohexyl acrylate, butylcyclohexyl acrylate, benzyl acrylate; methacrylic acid, ethyl methacrylate, propyl methacrylate, butyl methacrylate,
isobutyl methacrylate, t-butyl methacrylate,
Methacrylic acid or methacrylic acid esters such as 2-ethylhexyl methacrylate, cyclohexyl methacrylate, t-butylcyclohexyl methacrylate, phenyl methacrylate, benzyl methacrylate: styrene,
Aromatic vinyl compounds such as vinyl toluene, α-methylstyrene, monochlorostyrene, dichlorostyrene;
Cinnamic acid esters such as methyl cinnamate; maleic anhydride;
Imides such as maleimide and phenylmaleimide; examples include acrylonitrile, methacrylonitrile, etc. Preferred ethylene monomers for the present invention include methyl acrylate, ethyl acrylate, cyclohexyl methacrylate, t-butylcyclohexyl methacrylate, Styrene and maleic anhydride.

The weight average molecular weight of the acrylic resin of the present invention is 50,000 to 50
0,000, preferably 70,000 to 350,000. When the weight average molecular weight is less than 50,000, there is little improvement in strength even if the structural unit (I) is introduced, and when the weight average molecular weight exceeds 500,000, molding is difficult. The quality is poor and it is not practical.

In order to polymerize the acrylic resin of the present invention, conventionally known methods such as bulk polymerization, solution polymerization, and suspension polymerization can be used.

The polymerization initiator has the general formula (B);
z, Rx, Ra represent hydrogen, an alkyl group having 1 to 5 carbon atoms, a cyclohexyl group, or a phenyl group) 3 or more repeating units, preferably 5 to 30
Although an initiator having 100% or more may be used alone, any initiator commonly used in radical polymerization, such as an azo compound such as azobisisobutyronitrile, benzoyl peroxide, lauroyl peroxide, t-butyl-peroxy- It may be used in combination with an organic peroxide such as 2-ethylhexanoate.

Further, any molecular weight regulator generally used in radical polymerization can be used, and mercaptan compounds such as butyl mercaptan, octyl mercaptan, dodecyl mercaptan, and 2-ethylhexyl thioglycolate are particularly preferred.

The polymerization temperature is not particularly limited, but it is usually selected in the range of 20 to 160°C. It is preferable to control the temperature within the range of 10-hour half-life temperature of the agent + 70°C) because it is easy to introduce long-chain alkyl groups into the acrylic resin.

Note that the decomposition temperature indicating a 10-hour half-life of the organic peroxide is defined as a solvent relatively inert to radicals,
For example, an experiment in which the solution is dissolved in toluene or benzene at a concentration of 0.1 mol/l, sealed in a nitrogen-substituted glass tube, immersed in a constant temperature bath, and thermally decomposed is repeated by changing the temperature of the constant temperature bath. It can be determined according to the method described in JP-A-60-13805.

In the present invention, the residual monomer in the acrylic resin is 1.
It is 5% by weight or less, preferably 1.0% by weight or less, more preferably 0.6% by weight or less.

When the residual monomer exceeds 1.5% by weight, the heat resistance of the resin tends to decrease, and furthermore, voids tend to occur in the molded product.

The acrylic resin of the present invention may contain conventionally known additives depending on the purpose, such as various antioxidants, heat stabilizers, ultraviolet absorbers, metal sequestering agents, lubricants, mold release agents, plasticizers, etc. Antistatic agents, flame retardants, preservatives, paints, pigments, etc. can be added.

Various useful molded products can be obtained from the acrylic resin of the present invention by molding methods well known in the field of plastics technology, such as extrusion molding, injection molding, and compression molding.

Since the acrylic resin of the present invention has excellent moldability, it is particularly advantageous in fields that require dimensional accuracy, fields that require high-speed molding, and the like.

(Example) Next, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to the following Examples.

In addition, in each example, various analyzes and physical property evaluations of the polymer were performed by the following methods.

(a) Composition of structural unit (II): Quantified by pyrolysis gas chromatography method.

(b) Weight average molecular weight: Measured by gel vermini-silane chromatography and calculated from a standard polystyrene calibration curve.

(c) Residual monomer: Quantified by gas chromatography.

(d) Bending test: Measured according to ASTM D-790.

It was measured using

(f) Confirmation and quantification of structural unit (1): After dissolving 2 g of polymer in 80 d of methylene chloride, 5001
The polymer was dropped into d of n-hexane to precipitate the polymer, filtered, and further washed twice with 100 d of n-hexane. This polymer was dried at 60° C. for 24 hours under a reduced pressure of 10 mmHg, and c-NMR was measured under the following conditions.

Equipment: JNM-GX270 manufactured by JEOL Ltd. Sample conditions: Solvent pyridine-d.

Polymer concentration 2Qwt% Sample tube 10mmφ Measurement conditions: Complete decoupling mode (BGM) PD = 2.5 seconds, 5 can = 100,000 times Temperature 100'C The peak derived from the carbon of the methylene group of the long alkyl chain is 30 Appears at .5 ppm. This peak allows confirmation of the presence or absence of the structural unit (I) in the polymer.

The quantitative determination of the structural unit (1) is based on the ratio of the peak area of 30.5 ppm to the peak area of 16 to 23 ppm attributed to the α-methyl group of the structural unit (II), and the calibration curve detailed below. It can be calculated from the composition of structural unit (II).

Creation of a calibration curve> A mixture of methyl methacrylate and initiator (10 hour half-life 64.4°C) was heated at 65°C for 30 minutes.
Polymerization was carried out for a period of time to obtain a granular polymer. A purified polymer was obtained from this granular polymer by the same purification method as described above.

Several types of purified polymers were obtained by changing the amount of the charged initiator = the amount of structural unit (1) and the structural unit (II) in the purified polymer
) was determined as follows.

The amount of initiator in the three liquids obtained in the purification process was determined by iodometric titration (
The amount obtained by subtracting this amount from the amount of initiator charged is the amount of structural unit (1) present in the purified polymer. Furthermore, the amount of structural unit (II) in the purified polymer is determined by correcting the polymerization rate of the polymer with the amount of residual monomer determined by gas chromatography.

Next, the purified polymer was subjected to IICNMR measurement under the same conditions as described above.
．． The area ratio of the peak area at 5 ppm was determined, and a calibration curve was created.

(Example solution shown in Table 1): 2,500 g of water was added to 6,250 g of water in a 101 separable flask.
g, suspended in a suspension phase consisting of 25 g of polypotassium methacrylate, and polymerization was initiated at 70 ° C. 0 24 days after the start of polymerization
After 0 minutes, the polymerization temperature was raised to 95° C., and the reaction was continued for another 60 minutes. After the reaction was completed, it was cooled, filtered, washed, and dried to obtain a bead-like polymer. 30mm of this bead-like polymer
It was pelletized using an extruder with a φ vent.

When a test piece obtained by injection molding from this pellet was subjected to a bending test, the stress-strain curve showed a yield point, and stress whitening was observed in the test piece. In addition, pellets were used for various analyses. The results are shown in Table-2.

(Examples 2 to 8, Comparative Examples 1 to 4) The same procedure as in Example 1 was carried out except that the formulation was changed as shown in Table 1. The results are shown in Table-2.

(Example 9) A solution having the composition shown in Table 1 was continuously supplied to a sealed pressure vessel with a total volume of 1101, and the temperature was 120°C and the residence time was 1.
After polymerization for 80 minutes, the mixture was continuously extruded while removing volatile components to obtain pellets.

The physical properties were evaluated and analyzed in the same manner as in Example 1 using this pellet. The results are shown in Table-2.

(Comparative Example 5) Except for changing the formulation IjItc as shown in Table 1,
It was carried out in the same manner as in Example 9. The results are shown in Table-2.

(Effects of the Invention) In the present invention, by creating a new resin composition in which a specific amount of long-chain alkyl groups are introduced into the acrylic resin, the properties inherent to the acrylic resin such as transparency, high rigidity, and chemical resistance are maintained. It can be made to have excellent strength and moldability without impairing the properties.

Furthermore, the novel acrylic resin of the present invention has both a yield point and a breaking point in a bending stress test, and has particularly excellent resistance to breaking.

(Haka121)

Claims (2)

[Claims] (1) General formula (A): ▲There are mathematical formulas, chemical formulas, tables, etc.▼...(A) (In the formula, l, m, and n are integers from 1 to 20, R_1, R
_2, R_3, R_4 represent hydrogen, an alkyl group having 1 to 5 carbon atoms, a cyclohexyl group, or a phenyl group), 50 to 100% by weight of methyl methacrylate, and methyl methacrylate. Constituent unit (I
I), and the constituent unit (I) is 0.0% with respect to the constituent unit (II).
01 to 10% by weight, and the weight average molecular weight of the resin is 50,000 to 500,000. (2) The ethylene monomer copolymerizable with methyl methacrylate is an ethylene monomer selected from the group of methyl acrylate, ethyl acrylate, cyclohexyl methacrylate, t-butylcyclohexyl methacrylate, styrene, and maleic anhydride. The acrylic resin according to claim 1, characterized in that: