JPH04239511A - Styrenic resin having good moldability - Google Patents

Abstract

PURPOSE:To provide the subject styrenic resin having a wide molding temperature range, an excellent balance between the moldability and strength of the resin and good moldability at low temperatures without causing the deterioration of the surfaces of molded products and the lowering of the productivity. CONSTITUTION:The objective styrenic resin comprising constituent units of formula I (R1 is H, methyl; R2 is H, 1-5C alkyl) and formula II (R3 is H, methyl; R4 is 1-3C alkyl; wherein when R3 is methyl, R4 is 2-8C alkyl), having a viscosity of 15-80cp in a 10wt.% toluene solution at 25 deg.C, and containing the monomer, the dimer, the trimer, and the polymerization solvent in a total amount of <=0.8wt.%. The styrenic resin is produced by polymerizing 80-99.5mol% of a styrenic monomer (e.g. styrene) with 0.5-20mol% of an acrylate monomer (e.g. methyl acrylate) in the presence of an organic peroxide [e.g. 1,1-bis(t- butylperoxy)cyclohexane] in a solvent at an optimal temperature of <=170 deg.C.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a new styrenic resin. More specifically, the present invention relates to a specific proportion of styrenic structural units and acrylic esters (
The present invention relates to a styrene-based resin characterized by having excellent moldability by limiting the total amount of low-molecular-weight compounds to a specific amount or less.

0002

BACKGROUND OF THE INVENTION Styrene resins have been widely used as molding materials for household goods, electrical appliances, etc. because they have excellent transparency, moldability, and rigidity. For example, audio products such as audio cassette halves and plastic cases for storing cassette halves, office supplies for storing documents, etc., daily miscellaneous goods such as fish bowls, trays for storing clothes, bird cages, drinking cups, etc. It is used. Alternatively, in food packaging applications, styrene resin sheets, stretched sheets, and foams are often used.

[0003] In recent years, the required performance of molded products for various uses has become more sophisticated. For example, in the field of large molded products,
Styrenic resins with excellent fluidity are required to reproduce mold shapes, and it is desired to reduce running costs. Various improvements have been made to styrenic resins consisting only of styrene monomers. For example, it is a well-known method to use plasticizers to supplement moldability, but adding plasticizers can cause the so-called sweating phenomenon, in which the plasticizers adhere to the surface of the molded product or mold during molding. arise,
This is undesirable because it leads to a decrease in the quality of the molded product and a decrease in productivity due to mold cleaning. Moreover, the rigidity and strength are reduced.

On the other hand, in order to obtain fluidity suitable for large molded products with styrene resin, the general molding conditions are to increase the plasticizing resin temperature and mold temperature, but in this case, the cooling time becomes longer, leading to a decrease in productivity. Moreover, running costs increase, which is undesirable. There is also a demand for styrenic resins used in packaging applications that can be molded with higher productivity at lower temperatures than current molding conditions. In addition, sheets and films made of vinyl chloride resin, which have good moldability, are often used in various packaging applications, but due to recent environmental problems, resins that can replace vinyl chloride resin are required.

It is known to introduce a second monomer copolymerizable with the styrenic monomer in order to improve moldability. For example, it is known that in order to improve moldability, it is sufficient to introduce an acrylic ester. Japanese Patent Application Publication No. 5
Publication No. 9-221348 discloses that by using a styrene resin as a copolymer of styrene and butyl acrylate, the Vicat softening point is lowered and properties similar to vinyl chloride resin are imparted.

[0006]

[Problems to be Solved by the Invention] However, the styrenic resin containing butyl acrylate produced by thermal polymerization as disclosed in the above-mentioned publication contains low molecular weight compounds, and for example, molded products due to the sweating phenomenon This has led to problems such as a decrease in quality and a decrease in productivity due to mold cleaning, etc.

[0007]

[Means for Solving the Problems] In view of the current situation, the present inventors have conducted intensive studies, and have introduced a specific amount of acrylic ester (methacrylic ester) into the styrene monomer. The inventors have discovered that by limiting the total amount to a specific amount or less, a styrene resin with an excellent balance of moldability and strength can be obtained, and the present invention has been completed.

[0008] That is, the present invention The following general formula (A);

[0009]

[Chemical formula 3]

The following general formula (B);

[0011]

[C4]

It consists of the structural unit shown as [0012], and the structural unit (
The ratio of A) and (B) is (A): 80 to 99.5 mol% (B): 0.5 to 20 mol% (however, (A)
+ (B) = 100 mol%) at 25°C
The viscosity of the 10% by weight toluene solution is 15 centipoise or more and 80 centipoise or less, and the total amount of monomer, dimer, trimer, and polymerization solvent is 0.8% by weight or less. It provides styrenic resins.

The present invention will be explained in detail below. The degree of polymerization of the styrenic resin of the present invention is in the range of 15 centipoise to 80 centipoise, more preferably 20 centipoise to 70 centipoise, based on the viscosity of a 10% by weight toluene solution at 25°C, taking into account the shape of the molded product, the purpose of use, etc. Set in centipoise range. If the viscosity of the 10% by weight toluene solution is less than 15 centipoise, it is not preferable because it is difficult to adjust the molecular weight during production. If the viscosity of the 10% by weight toluene solution exceeds 80 centipoise, the productivity of the styrene resin will be poor and the moldability of the styrene resin will be extremely poor, making it impractical.

[0014] The amount of structural unit (B) is 0.5 to 20 mol.
% range. More preferably, it is in the range of 2 to 18 mol%, and still more preferably in the range of 2 to 15 mol%. If it exceeds 20 mol%, the rigidity of the styrene resin will decrease, heat resistance will decrease significantly, and productivity will deteriorate. Moreover, if it is less than 0.5 mol%, the effect of improving moldability will not be exhibited.

The structural unit (A) in the styrenic resin of the present invention
For example, styrene, α-methylstyrene, p-methylstyrene, pt-butylstyrene, etc. can be used as the styrenic monomer. These styrene monomers can be used alone or in combination. In order to introduce the structural unit (B), for example, as an acrylic ester (methacrylic ester) monomer, methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, se
c-butyl, ethyl methacrylate, n-propyl methacrylate, n-butyl methacrylate, sec-butyl methacrylate, n-pentyl methacrylate, etc. can be used. These acrylic ester (methacrylic ester) monomers can be used alone or in combination.

The monomers, dimers, and trimers contained in the styrenic resin of the present invention are styrene monomers and styrene dimers that cause mold suet, so-called unpleasant odor. , styrenic trimer, acrylic ester (
methacrylic acid ester) monomer, acrylic acid ester (
methacrylic acid ester) dimer, acrylic acid ester (
methacrylic acid ester) trimer, styrenic-acrylic ester (methacrylic ester) dimer, and styrene-based acrylic ester (methacrylic ester) trimer. The total amount of these monomers, dimers, trimers, and polymerization solvent must be 0.8% by weight or less. Preferably it is 0.75% by weight or less. If the amount exceeds 0.8% by weight, defects such as mold sweat may occur during molding, reducing productivity.

Further, the total amount of styrene monomers and acrylic acid ester monomers contained in the styrenic resin of the present invention is preferably 0.2% by weight or less. More preferably, it is 0.1% by weight or less. If it exceeds 0.2% by weight, it will cause a bad odor during molding. Furthermore, when the molded product is used as a food packaging material, it is not preferable in terms of food hygiene. In order to obtain the styrenic resin of the present invention, a mixed solution of styrene monomer and acrylic ester (methacrylic ester) monomer is adjusted so as to obtain the desired composition ratio and degree of polymerization of the styrene polymer. 0.005 to 2.0 parts by weight of an organic peroxide commonly used for polymerizing styrenic resins is added per 100 parts by weight of this monomer mixture, and polymerization is carried out at an optimum polymerization temperature of 170° C. or lower. Alternatively, the polymerization may be continued by mixing with a polymer solution of one or more of styrene monomers and acrylic ester (methacrylic ester) monomers polymerized in another reactor. good. In addition, at this time, a styrene monomer and/or an acrylic ester (methacrylic ester) monomer is added as necessary to obtain the desired composition ratio and degree of polymerization of the styrene polymer, and the optimum Polymerize at a certain polymerization temperature and recover the styrenic resin.

At this time, it is also possible to use a polymerization solvent such as ethylbenzene, toluene, xylene, etc. Furthermore, organic peroxides commonly used in the polymerization of styrenic resins can be added during the polymerization. As the polymerization method, the bulk polymerization method, solution polymerization method, suspension polymerization method, emulsion polymerization method, etc., which are commonly used in the production of styrenic resins, are used. or,
Either a batch polymerization method or a continuous polymerization method can be used.

In this case, there is no particular restriction on the polymerization reactor, and a complete mixing type reactor or a tubular reactor, which are commonly used for the polymerization of styrene resins, may be used. For this purpose, a complete mixing reactor is preferably used. The recovery equipment is not particularly limited, and equipment generally used for the production of styrenic resins is used, and the collection equipment is designed to maintain appropriate amounts of monomers, dimers, trimers, and polymerization solvents. The resin treatment temperature, degree of vacuum, etc. may be set within a range that does not cause quality deterioration.

[0020] The ratio of structural units (A) and (B) is determined by the following method. After dissolving the styrene resin in 10 times the amount of methyl ethyl ketone, the styrene polymer is precipitated while slowly adding it to the same amount of methanol. This styrenic polymer is dried at 200° C. under reduced pressure of 5 mmHg for 30 minutes. Using the styrenic polymer thus pretreated, 1H is measured using JNM-GX270 FT-NMR manufactured by JASCO Corporation under the conditions described below.

(1H measurement) Pulse width = 8.4 μs Data points = 16384 Repetition time = 7.559 seconds AD converter = 16 bits Number of integration = 10,000 Sample concentration = 10 wt% Solvent = 1, 1, 2, 2 -tetrachloroethane-(d2)
Sample tube = 5 mm Measurement temperature = 120°C A peak derived from the hydrogen of the phenyl group of the structural unit (A) appears at 6.2 to 7.4 ppm. A peak derived from hydrogen in the structural unit (B) appears at 3.4 to 4.2 ppm. The mol% of the structural unit (A) and the structural unit (B) is determined from the peak area ratio.

The amount of monomer and polymerization solvent contained in the styrenic resin of the present invention is determined by dissolving the styrene resin in N,N-dimethylformamide and measuring this solution by gas chromatography under the following conditions. . Note that each monomer and polymerization solvent are used as standard samples. (Gas chromatography conditions) Column: PEG-20M 30% on Chromosolve W, 60/80, 3.0mmφ x 3m Column temperature: 110°C Vaporization chamber temperature: 250°C Detector temperature: 250°C Carrier gas: N280ml/min Detector: FID The amount of dimer and trimer contained in the styrenic resin of the present invention can be determined by dissolving the styrenic resin in methyl ethyl ketone and then precipitating the styrenic polymer while slowly adding methanol. The supernatant solution at this time is measured by gas chromatography under the following conditions. Note that a styrene dimer and a styrene trimer are used as standard samples.

(Gas chromatography conditions) Column: Silicon DC410 20% on Chromosolve W, AW, DMCS, 80/100, 2.6 mmφ
×1m, column temperature: 140℃→240℃, 12℃/min
Vaporization chamber temperature: 250℃ Detector temperature: 250℃ Carrier gas: N240ml/min Detector: FID

[0024]

EXAMPLES The present invention will be explained in detail below using examples. The present invention is not limited in any way by these Examples. The physical property test methods in Examples are described below. Melt flow rate (MFR): ISO R1133
According to.

Vicat Softening Point (VICAT): ASTM
Conforms to D1525. Tensile strength: According to ASTM D638.

[0026]

[Examples 1 to 3, Comparative Examples 1 to 3] Using the following equipment,
Polymerizes styrene resin. The polymerization reactor is a complete mixing type reactor, and has a capacity of 30 L, and the reaction solution volume can be varied in the range of 5 to 25 L. A gear pump is installed at the outlet of the polymerization reactor and recovery system. The polymerization solution leaving the polymerization reactor is led to a preheater. The preheater has a built-in static mixer and has a capacity of 0.8L. 24 with preheater
After being heated to 0°C, it is led to a recovery device kept at 240°C, where it is devolatilized under a vacuum of 10 mmHg and pelletized.

Polymerization is carried out under the polymerization conditions shown in Table 1. The polymer concentration in the polymerization solution at the reactor outlet is also shown in Table 1. The product is collected 48 hours after the start of polymerization and its physical properties are evaluated. The physical property evaluation results are shown in Table 2.

[0028]

Comparative Example 4 Polymerization was carried out in the same manner as in Example 2, except that the degree of vacuum in the recovery device was 50 mmHg. The physical property evaluation results are shown in Table 2.

[0029]

[Example-4] Using the styrene resin used in Example-1, an injection molding machine IS800B-75 (Toshiba Machine Co., Ltd.) was used, the injection pressure was 100 kg/cm2, the mold temperature was 30°C, and the cooling time was 15 seconds. The tray shown in Fig. 1 was molded under the conditions.At this time, the injection temperature was varied to determine the lowest temperature at which the tray could be molded.Table 3 shows the results.

Next, a 40 g steel ball was dropped onto the center of this tray, the height at which cracking occurred was examined, and the fracture energy was determined. The results are also shown in Table 3. In addition, the appearance of molded products after continuous shot molding was compared. The results are also shown in Table 3.

[0031]

[Example 5] Physical properties were evaluated in the same manner as in Example 4, except that the styrene resin used in Example 2 was used. The results of the evaluation are shown in Table 3.

[0032]

[Example 6] Physical properties were evaluated in the same manner as in Example 4, except that the styrene resin used in Example 3 was used. The results of the evaluation are shown in Table 3.

[0033]

Comparative Example 5 The physical properties were evaluated in the same manner as in Example 4, except that the styrene resin used in Comparative Example 1 was used. The results of the evaluation are shown in Table 3.

[0034]

Comparative Example 6 The physical properties were evaluated in the same manner as in Example 4, except that the styrene resin used in Comparative Example 2 was used. The results of the evaluation are shown in Table 3.

[0035]

Comparative Example 7 The physical properties were evaluated in the same manner as in Example 4, except that the styrene resin used in Comparative Example 3 was used. The results of the evaluation are shown in Table 3.

[0036]

[Comparative Example-8] Physical properties were evaluated in the same manner as in Example-4, except that the styrene resin used in Comparative Example-4 was used. The results of the evaluation are shown in Table 3.

[0037]

[Table 1]

[0038]

[Table 2]

[0039]

[Table 3]

[0040]

[Effects of the Invention] According to the present invention, a styrenic resin having an excellent balance of moldability and strength is provided. In addition, the styrenic resin of the present invention has superior moldability at lower temperatures than conventionally used styrene resins, and does not deteriorate the surface of molded products and reduce productivity, such as when adding a plasticizer. I won't invite you.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of trays molded in Examples 4 to 6 of the present invention and Comparative Examples 5 to 8.

Claims (1)

[Claims] [Claim 1] Consisting of a structural unit represented by the following general formula (A); [Chem. 1] The following general formula (B);
The ratio of (A): 80 to 99.5 mol% (B): 0.5 to 20 mol% (however, (A)
+ (B) = 100 mol%) at 25°C
The viscosity of the 10% by weight toluene solution is 15 centipoise or more and 80 centipoise or less, and the total amount of monomer, dimer, trimer, and polymerization solvent is 0.8% by weight or less. Styrenic resin.