JPH0436305A - Impact-resistant styrenic resin - Google Patents

Abstract

PURPOSE:To prepare the title resin excellent in strengths, flowability, and gloss by keeping the mol.wt. of a styrenic resin constituting a continuous phase, the kind and content of a rubber as an impact modifier, the particle size of the rubber, and the degree of swelling and gel content of the resin each in a specified range. CONSTITUTION:An impact-resistant styrenic resin wherein graft rubber particles are dispersed in a continuous phase comprising a styrenic resin, the rubber being a plybutadiene contg. 90mol% or higher cis-1,4 bonds and contained in an amt. of 5-15wt.%, wherein the wt.-average mol.wt. of the styrenic resin is 150000-250000; the vol.-average particle size of the graft rubber particles is 1.3-2.3mum; the degree of swelling of the resin is 9 or higher; and the ratio (GEL/PBD) of the gel content (GEL) of the resin to the rubber content (PBD) is 2-3. The resin has an excellent quality balance among practical impact strength, moldability, and surface gloss and is very useful in the areas of a weak-currentic appliance, a business machine, and sundris.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to impact-resistant styrenic resins with excellent strength, fluidity, and gloss, and more particularly, to the molecular weight and toughening of continuous styrenic polymers. The type and content of the rubber used as the agent, the particle size of the grafted rubber particles dispersed in the resin, the degree of swelling and gel content of the resin are within specific ranges, and the practical impact resistance is achieved. Molding processability 1: Concerning impact-resistant styrenic resin with excellent surface gloss.

[Prior Art] Conventionally, since styrene resin is hard and brittle, it has been difficult to improve the resistance by blending a rubbery elastic material with a styrene resin or by polymerizing a styrene monomer in the presence of a rubbery elastic material. It has been improved by making it into an impact-resistant styrene resin.

Molded products made from impact-resistant styrene resin using injection molding are usually used for light electrical equipment and office equipment.

Industrial fields such as miscellaneous goods, specifically television and radio.

Used in housings for cleaners, air conditioners, etc. Recently, in the field of application of injection molded products, especially in the field of large molded products, a high quality balance such as high impact resistance, moldability, heat resistance, and high gloss is required for impact-resistant styrene resins. has been done.

Various proposals have been made to improve the individual properties of styrenic resins, but none of these proposals is necessarily satisfactory as a method for obtaining impact-resistant styrenic resins with a good balance between qualities. It wasn't something.

As is well known, to improve the impact resistance of styrene resin,
It is effective to increase the content of rubbery elastic material contained in styrenic resin, but as the content of rubbery elastic material increases, the viscosity of the styrenic monomer solution gradually increases. However, it has disadvantages in terms of stirring or transportation of the polymerization solution in industrial production. In addition, from the viewpoint of physical properties, impact-resistant styrene resins with a high content of rubber-like elastic material are unfavorable in terms of the balance of physical properties, as the rigidity, that is, the tensile strength and bending strength, decreases significantly and the resin becomes weak. .

Additionally, in order to improve moldability, it is generally known to add a plasticizer such as white mineral oil or an internal lubricant such as stearic acid, but adding a large amount of these may prevent a decrease in heat resistance. There were no drawbacks.

[Problems to be Solved by the Invention] Therefore, as a result of intensive studies to solve these drawbacks, the present inventors have developed an impact-resistant material made by dispersing grafted rubber particles in a styrene polymer. In styrenic resins, adjustments are made to the molecular weight of a specific continuous styrenic polymer, the type and content of a specific rubber, the particle size of a specific grafted rubber particle, and the degree of swelling and gel content of a specific resin. As a result, we have completed an impact-resistant styrenic resin that has excellent impact resistance, moldability, and surface gloss for practical use.

[Means for Solving the Problems] That is, the present invention provides a continuous styrenic polymer containing:
In an impact-resistant styrenic resin containing dispersed grafted rubber particles, and the rubber is polybutadiene with cis-1,4 bonds of 90 mol% or more and the content thereof is 5 to 15% by weight, (A) The weight average molecular weight of the continuous styrenic polymer is 1
50,000 to 250,000 (B) The volume average particle size of the grafted rubber particles is 1.3
~2.3 μm (C) The degree of swelling of the resin in toluene is 9 or more (D) The ratio of gel content (GEL) to rubber content (PBD) of the resin (G
It is an impact-resistant styrenic resin characterized by having an EL/PBD) of 2 to 3.

The present invention will be explained in detail below.

In the present invention, the continuous styrenic polymer is a single or copolymer of polystyrene, polyα-methylstyrene, polyvinyltoluene, polyt-butylstyrene, etc., or a copolymer with acrylonitrile, methyl methacrylate, etc. It may be.

In the present invention, the rubber of the grafted rubber particles dispersed and contained in the continuous styrenic polymer contains cis 1
, 4 bonds of 90 mol% or more is used. In general, polybutadiene can produce impact-resistant styrenic resins with superior low-temperature impact resistance compared to styrene-butadiene copolymer rubber, which is also used to improve the impact resistance of styrenic resins. It is preferable because However, if polybutadiene with low cis-1,4 bonds (less than 90 mol%) is used, the impact resistance will be inferior if the moldability is the same, and the moldability will be inferior if the impact resistance is the same. The balance is bad.

The rubber content in the impact-resistant styrenic resin of the present invention is usually 5 to 15% by weight, preferably 7 to 10% by weight. If the rubber content is less than 5% by weight, practically satisfactory impact resistance cannot be obtained, and if it exceeds 15% by weight, the viscosity of the styrenic monomer solution in which the rubber is dissolved increases during production. This causes manufacturing problems.

In order to produce the impact-resistant styrenic resin of the present invention, polybutadiene/styrenic monomers obtained by dissolving polybutadiene in a styrenic monomer so that the polybutadiene content is 5 to 15% by weight. The polymerization can be carried out using a body solution as a raw material by a known polymerization method, such as a bulk polymerization method, a bulk-suspension polymerization method, or a solution polymerization method.

In the present invention, the polymerization temperature is preferably in the range of 80 to 170°C, and if it is less than 80°C, it will take a long time to obtain the desired impact-resistant styrenic resin with an excellent balance of physical properties.
If the temperature exceeds 170°C, the reaction rate becomes excessive and smooth polymerization control becomes difficult.

Further, in the present invention, a polymerization initiator such as an organic peroxide can also be used.

The weight average molecular weight of the continuous styrenic polymer in the impact-resistant styrenic resin of the present invention is usually in the range of 150,000 to 250,000, preferably in the range of 170,000 to 220,000. If the weight average molecular weight is less than 150,000, the impact resistance will be poor, and if it exceeds 250,000, the fluidity will be poor and the balance of physical properties will be poor. The molecular weight of the continuous styrenic polymer can be adjusted by adjusting the chain transfer agent, polymerization initiator, polymerization temperature, etc.

In the present invention, the particle size of the grafted rubber particles dispersed and contained in the continuous styrenic polymer is usually 1.3 to 2.3 pm, preferably 1.4 to 2 pm in terms of volume average particle size.
．． A range of 0 pm is desirable. Average volume particle size is 1.3pm
If it is less than 2.31, the impact resistance will be poor, and if it exceeds 2.31, the gloss will be poor and the balance of physical properties will be poor.

The particle size of the grafted rubber particles can be adjusted by adjusting the molecular weight of the rubber used during polymerization, the stirring speed during polymerization, etc.

In the present invention, the expansion degree of the resin in toluene is usually 9 or more, preferably in the range of 10 to 12. If the degree of swelling is less than 9, the impact resistance will be poor, which is not preferable. Note that if the degree of swelling exceeds 12, the improvement effect will be small.

Further, the present invention is characterized in that the ratio (GEL/PBD) of gel content (GEL) to rubber content (PBD) of the resin is 2 to 3. If GEL/PBD is less than 2, impact resistance will be poor, and if it exceeds 3, fluidity will be reduced. The degree of swelling and gel content can be adjusted by adjusting the type and amount of polymerization initiator, polymerization temperature, etc.

Furthermore, known additives such as plasticizers, lubricants, mold release agents, heat stabilizers, antioxidants, and antistatic agents may be added to the impact-resistant styrenic resin of the present invention, if necessary. can.

The impact-resistant styrenic resin of the present invention is ASTM D-2
Izotsu impact strength measured by 56 is 9.0 kg
- cm/cm or more and the melt flow index measured by ASTM D-1238 is 1.8 g/cm.
If the molding time is 10 minutes or more, the impact strength and moldability are excellent, and the surface gloss is also good.

In addition, the microstructure of the polybutadiene referred to in the present invention, the molecular weight of the continuous styrenic polymer, the particle size of the grafted rubber particles dispersed and contained in the continuous styrenic polymer, the swelling degree/gel content of the resin , Izod
) impact strength, melt flow index (MFI),
It is measured by the following method.

(1) Microstructure of polybutadiene Measured by Morello method using JASCO IR-810,
It is expressed as a ratio of absorbance of cis 1,4 bond, trans 1.4 bond, and vinyl 1.2 bond.

(2) Molecular weight of continuous styrenic polymer Column (GMH
- Measurement was carried out using 612 pieces in series, and the weight average molecular weight is shown.

(3) Particle diameter of crafted rubber particles Measured using a Coulter counter (TA-I [manufactured by Nikkaki Co., Ltd.] with an aperture of 301, and expressed as a volume average particle diameter.

(4) Swelling degree, gel content Accurately weigh approximately 2 g of resin (referred to as W), and add 50 mA of toluene.
Dissolves in +. Insoluble matter is separated using a centrifuge, the supernatant liquid is discarded, and the sample is weighed in a wet state (referred to as W2). Then, dry it in a vacuum dryer until it reaches a constant weight and weigh it (W3
) and is calculated using the following formula.

Swelling degree = W z / W a Gel content (%) = (W, /W, ) X100
(5) Izod impact strength ASTM D-
Measurements were made based on 256.

(Test piece: 12.7X 6.4X64mm)
(6) Melt flow index (MFI) ASTM
Measurements were made based on D-1238.

(Temperature = 200° C., Load: 5 kg) [Examples] The present invention will be described in more detail below with reference to Examples, but the present invention is not limited to these Examples.

Example 1 Capacity 50I! In the autoclave, high-cis polybutadiene (product name: Ubeball BR15H, manufactured by Ube Industries, Ltd.,
40 kg of a styrene solution in which 3.2 kg of cis-1,4 bond (97.5%) was dissolved and 28 g of tertiary dodecyl mercaptan were added, and the mixture was stirred at 250 rpm. After purging the inside of the autoclave with nitrogen gas, the autoclave was sealed and the temperature was raised. After polymerizing at 110° C. for 5 hours, the mixture was cooled to complete the preliminary polymerization.

Next, the capacity is 100I! During the autoclave, pure water
0kg, sodium dodecylbenzenesulfonate 0
．． 50 g of tertiary-butylperoxybenzoate were added to the system, and while stirring at 180 rpm, the prepolymerization solution containing 32 g of tertiary-butyl peroxybenzoate was added to the system. After purging with nitrogen, the system was sealed, heated, and heated to 115°C for 50 minutes.
Polymerization was carried out at 135° C. for 3 hours and then cooled.

After neutralization, dehydration, and drying according to conventional methods, the polymer was extruded using an extruder to obtain an impact-resistant styrenic resin in the form of a normal pellet. Table 1 shows the physical properties.

Example 2 The same procedure as in Example 1 was carried out except that 60 g of 4-methyl-2,4-diphenylpentene-1 was added to the prepolymerization liquid. Table 1 shows the physical properties.

Example 3 The same procedure as in Example 1 was carried out except that the stirring speed during prepolymerization was changed from 25 Orpm to 20 Orpm. Table 1 shows the physical properties.

Example 4 The same procedure as in Example 1 was carried out except that the amount of tert-butyl peroxybenzoate added to the prepolymerization solution was changed from 32 g to 62 g. Table 1 shows the physical properties.

Comparative Example 1 The same procedure as in Example 1 was carried out except that low cis polybutadiene (trade name Nidiene 55AS, manufactured by Mukasei Co., Ltd., 35% cis 1,4 bonds) was used instead of high cis polybutadiene. Table 2 shows the physical properties.

Comparative Example 2 The same procedure as in Example 1 was carried out except that 4 g of divinylbenzene was added to the prepolymerization liquid. Table 2 shows the physical properties.

Comparative Example 3 The same procedure as in Example 1 was carried out except that 120 g of 4-methyl-2,4-diphenylpentene-1 was added to the prepolymerization liquid.

Table 2 shows the physical properties.

Comparative Example 4 The same procedure as in Example 1 was carried out except that the stirring number during prepolymerization was changed from 25 Orpm to 30 Orpm. Table 2 shows the physical properties.

Comparative Example 5 The same procedure as in Example 1 was carried out except that the stirring speed during prepolymerization was changed from 25 Orpm to 15 Orpm. Table 2 shows the physical properties.

Comparative Example 6 The same procedure as in Example 1 was carried out except that the amount of tert-butyl peroxybenzoate added to the prepolymerization solution was changed from 32 g to 20 g. Table 2 shows the physical properties.

Comparative Example 7 The same procedure as in Example 1 was carried out except that the amount of tertiary-butyl peroxybenzoate added to the prepolymerization solution was changed from 32 g to 96 g. Table 2 shows the physical properties.

Table 1 (Note) The measurement method is shown below.

■Izod impact strength ■Melt flow index (MFI) ■HDT (
(deflection temperature under load) ■Gloss: ASTM D-256: ASTM D-1238: ASTM D-648: JIS Z-8741 [Effects of the Invention] As explained above, the impact-resistant styrenic resin of the present invention is suitable for practical use. It has an excellent quality balance of impact resistance, moldability, and surface gloss, making it extremely useful in industrial fields such as light electrical equipment, office equipment, and miscellaneous goods.

Applicant: Denki Kagaku Kogyo Co., Ltd.

Claims (1)

[Claims] Contains grafted rubber particles dispersed in a continuous styrenic polymer, and the rubber has 90 cis-1,4 bonds.
In impact-resistant styrenic resins whose content is 5 to 15% by weight of polybutadiene of mol% or more, (A) the weight average molecular weight of the continuous styrenic polymer is 1
50,000 to 250,000 (B) The volume average particle size of the grafted rubber particles is 1.3
~2.3 μm (C) Resin swelling degree in toluene is 9 or more (D) Resin gel content (GEL) and rubber content (PB
An impact-resistant styrenic resin characterized in that the ratio (GEL/PBD) of D) is in the range of 2 to 3.