WO2004015008A1

WO2004015008A1 - Rubber-modified styrene resin composition

Info

Publication number: WO2004015008A1
Application number: PCT/KR2003/001348
Authority: WO
Inventors: Dae-San Jung; Yong-Yeon Hwang; Su-Yeon Na; Jong-Kuk Choi; Chan-Hong Lee
Original assignee: LG Chem Ltd
Current assignee: LG Chem Ltd
Priority date: 2002-08-13
Filing date: 2003-07-07
Publication date: 2004-02-19
Anticipated expiration: 2005-02-13
Also published as: KR20040015534A; DE60320109T2; JP4078350B2; US6946516B2; EP1529079A1; KR100463171B1; EP1529079B1; ATE391152T1; CA2465056C; CN1246382C; AU2003237071A1; US20050020737A1; CA2465056A1; JP2005521786A; DE60320109D1; CN1585801A

Abstract

A rubber-modified flame resistant styrene resin composition, which has superior heat stability and weather resistance to prevent discoloration and deterioration due to heat or light and is processed under various molding condition, is provided. The rubber-modified flame resistant styrene resin composition includes a rubber-modified styrene resin, flame retardant comprising compounds selected from a group consisting of tetrabromobisphenol-A-bis(2,3-dibromopropylether), hexabromocyclododecane and a mixture thereof, and brominated epoxy oligomer, and calcium stearate as a lubricant.

Description

RUBBER-MODIFIED STYRENE RESIN COMPOSITION

BACKGROUND OF THE INVENTION

(a) Field of the Invention

The present invention relates to a styrene resin composition having

superior heat stability and weather resistance, more particularly to a rubber-

modified flame resistant styrene resin composition that has superior heat

stability and weather resistance to prevent discoloration or deterioration due

to heat or light and surface appearance problems under various molding

conditions.

(b) Description of the Related Art

Styrene resins are used for various applications due to their superior

mechanical properties, electrical properties, and molding processibility.

However, styrene resins are combustible, and their flame resistance and

weather resistance are not enough for being used for electrical or automotive

components.

Flame retardants and flame retardant synergists are used to provide

flame resistance to styrene resins. Typically, a halogen flame retardant and

antimony trioxide flame retardant synergist are used. However, when a

halogen flame retardant is used to obtain a flame resistant resin, hydrogen

halide is generated from the halogen flame retardant by heat or light and

causes formation of a carbonyl group or a conjugated double bond,

crosslinkage, and breaking of molecular bonds, which are known as the cause of discoloration and deterioration of styrene resins. Therefore,

stabilizers like a light stabilizer, a U V stabilizer, and an anti-oxidant are added

to solve this problem.

Korea Patent Application No. 1998-044225 discloses use of halogen

compounds other than decabromodiphenyl ether and titanium dioxide to

improve the heat stability and weather resistance of rubber-modified resins.

However, because some flame retardants are limited in improving heat

stability and weather resistance, this method cannot be applied for office

furnishings. Additionally, as the shape of molding products becomes very

complex, surface appearance problems, such as gas silver and black streaks

are easily generated during injection molding due to decomposition gas.

Therefore, superior heat stability is required to prevent surface appearance

problems under various molding conditions.

Accordingly, there is a need for a rubber-modified flame resistant

styrene resin that has superior heat stability and weather resistance to

prevent discoloration or deterioration due to heat or light, and can be used for

various applications.

SUMMARY OF THE INVENTION

The present invention provides a rubber-modified flame resistant

styrene resin composition that has superior heat stability and weather

resistance to prevent discoloration or deterioration due to heat or light and

surface appearance problems under various molding conditions so that it can be used for wide applications.

According to one aspect of the present invention, a rubber-modified

flame resistant styrene resin composition comprises: a) 100 parts by weight of

a rubber-modified styrene resin; b) 0.2 to 20 parts by weight of a flame

retardant: and c) 0.1 to 3 parts by weight of calcium stearate as a lubricant.

The flame retardant comprises i) 0.1 to 10 parts by weight of compounds

selected from a group consisting of tetrabromobisphenol-A-bis(2,3-

dibromopropylether), hexabromocyclododecane and a mixture thereof; and ii)

0.1 to 10 parts by weight of a brominated epoxy oligomer.

According to another aspect of the present invention, a method for

preparing a frame retardant styrene resin composition, comprises

copolymerizing a rubber phase polymer and a vinyl aromatic monomer to

prepare a rubber-modified styrene resin; adding a flame retardant to 100

parts by weight of the rubber-modified styrene resin, the flame retardant

including: 0.1 to 10 parts by weight of compound selected from a group

consisting of tetrabromobisphenol-A-bis(2,3-dibromopropylether),

hexabromocyclododecane and a mixture thereof; and 0.1 to 10 parts by

weight of a brominated epoxy oligomer; and adding a lubricant including 0.1

to 3 parts by weight of calcium stearate to 100 parts by weight of the rubber-

modified styrene resin.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Hereinafter, the present invention is explained in more detail. According to exemplary embodiments of the present invention, when

a halogen flame retardant comprising a compound selected from a group

consisting of tetrabromobisphenol-A-bis(2,3-dibromopropylether),

hexabromocyclododecane and a mixture thereof, and a brominated epoxy

oligomer, and a lubricant comprising calcium stearate are added in a rubber-

modified styrene resin, the heat stability and weather resistance of a rubber-

modified flame resistant styrene composition are improved significantly.

The rubber-modified flame resistant styrene composition of the

present invention comprises 100 parts by weight of the rubber-modified

styrene resin, 0.2 to 20 parts by weight of the flame retardant and 0.1 to 3

parts by weight of calcium stearate lubricant. The 0.2 to 20 parts by weight

of flame retardant comprises 0.1 to 10 parts by weight of a compound

selected from a group consisting of tetrabromobisphenol-A-bis(2,3-

dibromopropylether), hexabromocyclododecane and a mixture thereof, and

0.1 to 10 parts by weight of brominated epoxy oligomer.

The rubber-modified styrene resin used in the present invention has a

rubber phase polymer of which particles are dispersed in a matrix and vinyl

aromatic monomers.

As the vinyl aromatic monomer, styrene compounds are

predominantly used, and a copolymer of styrene compound and compound

that can be copolymerized therewith can also be used. For the styrene

compound, styrene; a nucleus-alkyl-substituted styrene such as p- methylstyrene, 2,4-dimethylstyrene, or ethylstyrene; or an α-alkyl-substituted

styrene such as α-methylstyrene or α-methyl-p-methylstyrene can be used

alone or in combination. As the compound copolymerizable with the styrene

compound, a methacrylate ester such as methyl methacrylate or ethyl

methacrylate, unsaturated nitrile compound such as acrylonitrile or

methacrylonitrile, or maleic anhydride, etc. can be used.

For the rubber phase polymer, a rubber phase polymer comprising

polybutadiene, an acrylate or methacrylate, a styrene-butadiene-styrene

copolymer, a styrene-butadiene copolymer, polyisoprene, a butadiene-

isoprene copolymer, or a natural rubber, etc. can be used. Particularly,

polybutadiene or a styrene-butadiene copolymer is preferable, and

polybutadiene is more preferable. As the polybutadiene, a low-cis

polybutadiene, a high-cis polybutadiene, or a mixture thereof can be used.

Preferably, the rubber phase polymer is contained in an amount of 3

to 30 parts by weight, more preferably 4 to 15 parts by weight, based on 100

parts by weight of a rubber-modified styrene resin. If the content of the

rubber phase polymer is less than 3 parts by weight, the impact resistance

becomes insufficient, and, if it is over 30 parts by weight, the heat stability

may decrease, or a decrease in melt fluidity, gel formation, and discoloration

may be caused. Preferably, an average particle diameter of the rubber

phase particles is 0.5 to 6μm, and the glass transition temperature (T_g) of the

rubber phase polymer is -10°C or less. If the glass transition temperature is over -10°C, the impact resistance may decrease.

The rubber-modified styrene resin can be polymerized by bulk

polymerization, suspension polymerization, or emulsion polymerization.

Particularly, bulk polymerization is the most prevalent. In bulk

polymerization, after dissolving the rubber phase polymer in the vinyl aromatic

monomer, polymerization is conducted by adding a polymerization initiator

with stirring.

Tetrabromobisphenol-A-bis(2,3-dibromopropylether) and

hexabromocyclododecane, flame retardants used in the present invention,

are represented by the following Chemical Formula 1 and Chemical Formula

2, respectively. They offer flame resistance to the rubber-modified styrene

resin.

[Chemical Formula 1]

BrCH CHBrCH 0 OCH,CHBrCH,Br

[Chemical Formula 2]

Tetrabromobisphenol-A-bis(2,3-dibromopropylether) and

hexabromocyclododecane may be used in the rubber-modified flame resistant styrene resin composition alone or in combination.

The compounds selected from a group consisting of

tetrabromobisphenol-A-bis(2,3-dibromopropylether),

hexabromocyclododecane and a mixture thereof are preferably contained in

an amount of 0.1 to 10 parts by weight, more preferably 1 to 8 parts by weight,

based on 100 parts by weight of the rubber-modified styrene resin. If the

content is less than 0.1 parts by weight, flame resistance becomes insufficient,

and, if it exceeds 10 parts by weight, mechanical strength and heat stability

may be poor.

The brominated epoxy oligomer, another flame retardant used in the

present invention, is represented by the following Chemical Formula 3. It

offers flame resistance and heat stability to the rubber-modified flame

resistant styrene resin.

[Chemical Formula 3]

In Chemical Formula 3, n is an integer of 0 to 10.

The brominated epoxy oligomer is preferably contained in an amount

of 0.1 to 10 parts by weight, more preferably 0.5 to 8 parts by weight, based

on 100 parts by weight of the rubber-modified styrene resin. If the content is

less than 0.1 parts by weight, flame resistance and heat stability become poor, and, if it exceeds 10 parts by weight, mechanical strength may decrease.

Calcium stearate, a lubricant used in the present invention, is

represented by the following Chemical Formula 4:

[Chemical Formula 4]

Preferably, the calcium stearate is contained in an amount of 0.1 to 3

parts by weight, based on 100 parts by weight of rubber-modified styrene

resin. If the content is less than 0.1 parts by weight, the heat stability may

not be insignificantly improved, and, if it exceeds 3 parts by weight,

mechanical strength may be significantly reduced.

The rubber-modified flame resistant styrene resin composition of the

present invention may further comprise compounds selected from a group

consisting of antimony trioxide, antimony pentoxide and a mixture thereof as

a flame retardant synergist. The flame retardant synergist causes synergy

with halogen compounds used as flame retardants to further improve flame

resistance.

Preferably, the flame retardant synergist is contained in an amount of

0.01 to 15 parts by weight, based on 100 parts by weight of the rubber-

modified styrene resin. If the content is less than 0.01 parts by weight,

synergy with the halogen compound may be insignificant, and, if it exceeds

15 parts by weight, mechanical strength may be significantly reduced. In addition, the rubber-modified flame resistant styrene resin

composition of the present invention may further comprise other additives

such as a UV stabilizer and titanium dioxide, in order to improve weather

resistance.

For the UV stabilizer, 2-(2-hydroxy-5-methylphenyl)benzotriazole, 2-

(3,5-di-f-butyl-2-hydroxyphenyl)-5-chlorobenzotriazole or bis(2, 2,6,6-

tetramethyl-4-piperidinyl)sebacate, etc. can be used alone or in combination.

The UV stabilizer can be preferably used in an amount of 0.05 to 1 part by

weight, based on 100 parts by weight of the rubber-modified styrene resin. If

its content is less than 0.05 parts by weight, improvement in weather

resistance cannot be expected, and, if it exceeds 1 part by weight, the

weather resistance improvement effect will not be substantial considering the

added amount.

Titanium dioxide suppresses discoloration of the resin. It can be

used in an amount of 0.1 to 6 parts by weight, based on 100 parts by weight

of the rubber-modified styrene resin. If its content is less than 0.1 parts by

weight, the effect of suppressing discoloration of the resin may be

insignificant, and, if it exceeds 6 parts by weight, mechanical prosperities may

decrease.

The rubber-modified flame resistant styrene resin composition of the

present invention shows no discoloration or deterioration due to heat or light,

and has superior heat stability and weather resistance. In addition, it can be processed under various molding conditions without surface appearance

problems. Particularly, it can be used for light colored office furnishings.

Hereinafter, the present invention is described in more detail through

Examples and Comparative Examples. However, the following Examples

are only for the understanding of the present invention, and the present

invention is not limited by the following Examples.

EXAMPLE

Example 1

(Preparation of a rubber-modified styrene resin)

A monomer solution comprising 8 parts by weight of butadiene rubber,

77 parts by weight of styrene, and 15 parts by weight of ethylbenzene was

prepared. 0.02 parts by weight of 1 ,1-bis(f-butyl peroxy)-3,3,5-

trimethylcyclohexane was added to the monomer solution as a polymerization

initiator. The mixture solution was fed into a continuous polymerization

system equipped with four agitated reactors linked in series to conduct

continuous graft copolymerization. Temperature of the polymerization

system was 125°C at the inlet and 140^°C at the exit. The copolymerization

mixture solution was transferred to an evaporation tank to remove unreacted

monomer and solvent under the condition of 230 ^°C and 20 torr. The product

was pelletized to obtain a rubber-modified styrene resin (HIPS) comprising 8

wt% of rubber.

(Preparation of a rubber-modified flame resistant styrene resin) For 100 parts by weight of the above-prepared rubber-modified

styrene resin (HIPS) comprising 8 wt% of rubber, 4 parts by weight of

tetrabromobisphenol-A-bis(2,3-dibromopropylether) and 2 parts by weight of

brominated epoxy oligomer as a flame retardant, 1.5 parts by weight of

antimony trioxide as flame retardant synergist, 0.5 parts by weight of calcium

stearate as a lubricant, 0.1 parts by weight of an anti-oxidant, 3 parts by

weight of titanium dioxide, and 0.5 part by weight of a UV stabilizer were

added. The mixture was uniformly mixed using a Henschel mixer. Then, it

was extruded and pelletized using a twin screw extruder, and then injection-

molded into a specimen.

Examples 2 to 3 and Comparative Examples 1 to 5

The procedure of Example 1 was conducted with different

compositions and contents given in the following Table 1 to prepare rubber-

modified flame resistant styrene resins of the Examples 2 to 3 and

Comparative Examples 1 to 5.

Table 1

For the rubber-modified flame resistant styrene resins prepared in

Examples 1 to 3 and Comparative Examples 1 to 5, the heat stability, weather

resistance, and flame resistance were measured as follows. The results are

shown in Table 4.

a) Heat stability - The resins prepared in Examples 1 to 3 and Comparative Examples 1 to 5 were put in a Melt Indexer cylinder at 250 ^°C for

30 minutes, and then these resins were put in a beaker filled with distilled

water. The whiteness of the resins was evaluated with the naked eye

according to the standard given in Table 2.

Table 2

b) Weather resistance - Weather resistance was measured by ASTM

D4459 under the condition of Table 3:

Table 3

c) Flame resistance - Flame resistance was measured by ASTM

D3801 according to UL-94. Table 4

As shown in Table 4, it can be identified that the rubber-modified

flame resistant styrene resins of Examples 1 to 3 (which were prepared using

tetrabromobisphenol-A-bis(2,3-dibromopropylether),

hexabromocyclododecane, and a brominated epoxy oligomer as a flame

retardant and using calcium stearate as a lubricant according to the present

invention) showed superior heat stability, weather resistance, and flame

resistance, compared to those of Comparative Examples 1 to 5. In addition,

the resins of Comparative Examples 1 and 2, wherein brominated epoxy

oligomer flame retardant was not used, showed very poor heat stability and

weather resistance, and the resins of Comparative Examples 3 to 5 using zinc

stearate as a lubricant instead of calcium stearate showed very poor weather

resistance.

The rubber-modified flame resistant styrene resin composition of the

present invention shows no discoloration or deterioration due to heat or light,

and has superior heat stability and weather resistance. Also, it can be

processed under various molding conditions without surface appearance problems. Therefore, it can be used for light colored office furnishings.

While the present invention has been described in detail with

reference to the preferred embodiments, those skilled in the art will appreciate

that various modifications and substitutions can be made thereto without

departing from the spirit and scope of the present invention as set forth in the

appended claims.

Claims

WHAT IS CLAIMED IS:

1. A rubber-modified flame resistant styrene resin composition

comprising:

a) 100 parts by weight of a rubber-modified styrene resin;

b) 0.2 to 20 parts by weight of a flame retardant comprising:

i) 0.1 to 10 parts by weight of compound selected from a group

consisting of tetrabromobisphenol-A-bis(2,3-dibromopropylether),

hexabromocyclododecane and a mixture thereof; and

ii) 0.1 to 10 parts by weight of a brominated epoxy oligomer; and

c) 0.1 to 3 parts by weight of calcium stearate as a lubricant.

2. The rubber-modified flame resistant styrene resin composition

according to Claim 1 , wherein the rubber-modified styrene resin of a) is

prepared by copolymerization of a rubber phase polymer and a vinyl aromatic

monomer.

3. The rubber-modified flame resistant styrene resin composition

according to Claim 2, wherein the rubber phase polymer has an average

particle diameter of 0.5 to 6μm and a glass transition temperature (T_g) of -

10 ^°C or lower.

4. The rubber-modified flame resistant styrene resin composition

according to Claim 1 , wherein the brominated epoxy oligomer of b) ii) is

represented by the following Chemical Formula 3: [Chemical Formula 3]

wherein n is an integer of 0 to 10.

5. The rubber-modified flame resistant styrene resin composition

according to Claim 1, further comprising d) 0.01 to 15 parts by weight of

compound selected from a group consisting of antimony trioxide, antimony

pentoxide and a mixture thereof, as flame retardant synergist.

6. The rubber-modified flame resistant styrene resin composition

according to Claim 1 , further comprising e) 0.05 to 1 parts by weight of UV

stabilizer selected from a group consisting of 2-(2-hydroxy-5-

methylphenyl)benzotriazole, 2-(3,5-di-t-butyl-2-hydroxyphenyI)-5-

chlorobenzotriazole, bis(2,2,6,6-tetramethyl-4-piperidinyl)sebacate and a

mixture thereof.

7. The rubber-modified flame resistant styrene resin composition

according to Claim 1 , further comprising f) 0.1 to 6 parts by weight of titanium

dioxide.

8. A method for preparing a frame retardant styrene resin composition,

comprising:

copolymerizing a rubber phase polymer and a vinyl aromatic monomer to prepare a rubber-modified styrene resin;

adding a flame retardant to 100 parts by weight of the rubber-modified

styrene resin, the flame retardant including:

0.1 to 10 parts by weight of compound selected from a group

consisting of tetrabromobisphenol-A-bis(2,3-dibromopropylether),

hexabromocyclododecane and a mixture thereof; and

0.1 to 10 parts by weight of a brominated epoxy oligomer; and

adding a lubricant including 0.1 to 3 parts by weight of calcium

stearate to 100 parts by weight of the rubber-modified styrene resin.

9. The method according to Claim 8, further comprising:

adding a flame retardant synergist including 0.01 to 15 parts by weight

of compound selected from a group consisting of antimony trioxide, antimony

pentoxide and a mixture thereof, to 100 parts by weight of the rubber-modified

styrene resin.

10. The method according to Claim 8, further comprising:

adding 0.05 to 1 parts by weight of UV stabilizer selected from a group

consisting of 2-(2-hydroxy-5-methylphenyl)benzotriazole, 2-(3,5-di-t-butyl-2-

hydroxyphenyl)-5-chlorobenzotriazole, bis(2,2,6,6-tetramethyl-4-

piperidinyl)sebacate and a mixture thereof, to 100 parts by weight of the

rubber-modified styrene resin.

11. The method according to Claim 8, further comprising:

adding 0.1 to 6 parts by weight of titanium dioxide to 100 parts by weight of the rubber-modified styrene resin.

12. The method according to Claim 8, wherein copolymerizing a

rubber phase polymer and a vinyl aromatic monomer is performed by bulk

polymerization, suspension polymerization, or emulsion polymerization.

13. The method according to Claim 8, wherein copolymerizing a

rubber phase polymer and a vinyl aromatic monomer includes adding the

rubber phase polymer in an amount of 3 to 30 parts by weight, based on 100

parts by weight of the rubber-modified styrene resin.