DE69224841T2 - Flame retardant polyester resin composition - Google Patents

Description

Background of the invention

The present invention relates to a resin composition suitable for producing automotive parts, electrical and electronic components, general manufactured articles and the like, the resin composition having excellent moldability and giving molded articles having significant flame retardancy, heat distortion temperature, impact resistance, chemical resistance and weather resistance.

Polycarbonate resin is known to be a plastic material with the highest impact strength of all engineering plastics and satisfactory heat distortion temperature, and has a wide range of applications where these properties are of great value. However, this resin has some disadvantages, namely low chemical resistance, poor formability and thickness dependence of the impact strength.

On the other hand, thermoplastic polyester resins prove to be excellent in terms of chemical resistance and formability, but have poor properties in terms of impact resistance and dimensional stability.

In order to make the most of the desired properties of the respective resins and to compensate for their disadvantages, a variety of resin compositions have been proposed in the literature, e.g. in JP-B-36-14035, JP-B-39-20434, JP-B-55-9435, JP-B-62-37671, JP-B-62-34792, JP-B-62-13378, JP-A-62-295951, JP-A-63-83158 and JP-A-64-16859.

Thus, JP-B-36-14035 describes a thermoplastic material comprising a 4,4'-dioxydiarylalkane polycarbonate and polyethylene terephthalate. JP-B-39-20434 describes a resin composition comprising a 4,4'-dioxydiarylalkane polycarbonate, a polyolefin and a saturated polyester.

JP-B-55-9435 describes a thermoplastic resin composition comprising an aromatic polyester, an aromatic polycarbonate and a butadiene graft copolymer.

JP-B-62-37671 describes a thermoplastic resin composition comprising a saturated polyester resin, a polycarbonate resin and a polymer containing a polyacrylate rubber as main components.

JP-B-62-34792 describes a polycarbonate resin composition comprising a polycarbonate resin, a saturated polyester resin, a polyolefin resin and a vinyl polymer containing an acrylate rubber.

JP-B-62-13378 describes a polycarbonate resin composition comprising a polycarbonate resin, a saturated polyester resin, a polyolefin and an acrylate-methacrylate resin.

JP-A-62-295951 proposes a polycarbonate resin composition comprising a polycarbonate resin, an aromatic polyester resin and an acrylate-butadiene graft copolymer. JP-A-63-83158 describes a resin composition comprising an aromatic polycarbonate, a thermoplastic polyester, a thermoplastic graft copolymer and a polyolefin.

JP-A-64-16859 describes a flame-retardant polyester composition comprising a polyester, a halogenated polycarbonate oligomer, a halogenated phenoxy resin and an antimony compound.

However, none of these resin compositions is suitable for providing all the required properties for automotive parts, electrical/electronic components and other parts, namely, achieving sufficient impact resistance, heat distortion temperature, chemical resistance, weather resistance, rigidity and elongation at break. Therefore, there is a serious need for further improvements.

In addition, in some applications, such as automotive interior parts or electrical and electronic components, a flame retardant property is required for safety reasons. However, since the addition of a flame retardant may result in losses in terms of impact resistance, thermal distortion temperature, stiffness and elongation at break, no resin composition is currently available that is balanced in terms of its physical properties.

Summary of the invention

According to the invention, a resin composition is provided which has the required diverse properties which are not present in conventional resin compositions. The object of the invention is to provide a resin composition which is easy to mold and gives molded parts with improved flame retardancy, heat distortion temperature, impact resistance, resistance to chemicals and weather resistance.

The inventors have, after extensive investigations, found that the above object can be easily achieved by preparing a composition comprising a polycarbonate, a thermoplastic polyester and a halogenated phenoxy resin, optionally together with an impact modifier and an antimony compound in certain proportions. The present invention is based on the above investigations and findings.

The invention is therefore directed to a flame-retardant polyester resin composition containing the following components:

(A) 10 to 90% (wt. %, the same applies to the later statements) of a polycarbonate having an average molecular weight determined by viscosity of 10,000 to 60,000,

(B) 10 to 90% of a thermoplastic polyester,

(C) 0 to 40% of an impact modifier,

(D) 3.5 to 30 parts, based on 100 parts (parts by weight, the same applies to later statements) of the combination of (A), (B) and (C), of a halogenated phenoxy resin having a weight average molecular weight of 5,000 to 200,000, which has repeating structural chain units of the general formula (I)

wherein X represents a bromine atom or a chlorine atom, Y represents an alkylene group having 1 to 10 carbon atoms, an alkylidene group, a carbonyl group, -O-, -S- or -SO₂-, and

(E) 0 to 30 parts, based on 100 parts of the combination of (A), (B) and (C), of an antimony compound.

The polycarbonate which constitutes component (A) of the composition of the invention is a polycarbonate resin derived from a dihydric phenol and is generally obtainable by reacting a dihydric phenol with phosgene or a carbonic acid diester.

There are no restrictions on the type of dihydric phenol, but bisphenol A is particularly suitable for economic reasons.

The molecular weight, expressed as viscosity-average molecular weight, of the polycarbonate resin is preferably in the range of 10,000 to 60,000. If the molecular weight of the polycarbonate used is less than 10,000, sufficient impact resistance and chemical resistance cannot be obtained, while if a polycarbonate having a molecular weight of more than 60,000 is used, the moldability of the composition tends to be impaired.

According to the invention, the proportion of polycarbonate is 10 to 90%, preferably 20 to 80% and in particular 30 to 70%, based on the total weight of components (A) to (C). If the proportion is less than 10%, there are losses in terms of impact strength, thermal stability, dimensional stability and flame retardant properties. On the other hand, If more than 90% polycarbonate is used, the chemical resistance and deformability are reduced.

The thermoplastic polyester resin (B) to be used in the invention is a homopolymer or copolymer obtainable by reacting an aromatic dicarboxylic acid or an ester-forming derivative thereof with a diol or an ester-forming derivative thereof.

The solution viscosity of this thermoplastic polyester resin, determined as the inherent viscosity (LV) at a concentration of 0.5 g/dl in phenol/tetrachloroethane (1:1, w/w) at 25ºC, is preferably in the range of 0.3 to 2.0. If the inherent viscosity is less than 0.3, there is a tendency to deteriorate in impact resistance and chemical resistance, while if the LV is more than 2.0, there is a tendency to deteriorate in moldability.

As preferred examples of such a thermoplastic polyester resin, there may be mentioned polyethylene terephthalate, polypropylene terephthalate, polytetramethylene terephthalate and polycyclohexanedimethylene terephthalate. Particularly preferred are polyethylene terephthalate and polytetramethylene terephthalate.

The proportion of thermoplastic polyester is according to the invention 10 to 90%, preferably 20 to 80% and in particular 30 to 70%, based on the sum of components (A) to (C). If the proportion is less than 10%, there are losses in terms of chemical resistance and deformability. On the other hand, the use of this composition in a proportion of more than 90% leads to a reduction in impact resistance, heat distortion temperature, dimensional stability and flame retardancy. If necessary, an impact resistance modifier (component C) can be incorporated into the resin composition according to the invention.

Examples of such an impact modifier which may be used in the practice of the invention are olefinic polymers, Core/shell graft polymers, polyester elastomers and the like, although the invention is not limited thereto.

The degree of polymerization of the aforementioned polyolefin is not particularly critical, but in general, a polyolefin having a melt index in the range of 0.05 to 50 g/10 min can be selectively used.

As specific examples of such a polyolefin, there may be mentioned homopolymers and copolymers such as linear low-density polyethylene, low-density polyethylene, high-density polyethylene, polypropylene, ethylene-propylene copolymers, ethylene-propylene-diene terpolymers and the like.

The aforementioned core/shell graft polymers can be obtained by graft polymerization of a vinyl compound with a rubbery elastomer.

The rubbery elastomer which can be used in the preparation of the core/shell graft polymer is preferably an elastomer having a glass transition temperature of not more than 0ºC and in particular not more than -40ºC.

As specific examples of such rubbery elastomers, there may be mentioned diene rubbers such as polybutadiene, polybutadiene-styrene copolymers, butadiene-butyl acrylate copolymers and the like, polyacrylate rubbers such as polybutyl acrylate, poly(2-ethylhexyl acrylate) and the like, olefin rubbers such as ethylene-propylene copolymers, ethylene-propylene-diene terpolymers and the like. In view of weather resistance and impact resistance, the use of a butadiene-butyl acrylate copolymer is advantageous.

The proportion of butyl acrylate in the butadiene-butyl acrylate is preferably 50 to 70%. If the proportion of butyl acrylate in the copolymer is less than 50%, sufficient weather resistance is not achieved, while if the proportion of butyl acrylate is more than 70%, there is a tendency to impair the impact resistance and in particular the impact resistance at low temperatures.

The average particle size and gel content of the rubbery elastomer are not particularly limited, but preferably the average Particle size 0.05 to 2.0 μm and the preferred gel content 10 to 90%.

The vinyl compound that can be used in the preparation of the core/shell graft polymer includes aromatic vinyl compounds, vinyl cyanides, acrylic esters, methacrylic esters and the like. These monomers can be used individually or in combination with each other.

Preferred examples include styrene for aromatic vinyl compounds, acrylonitrile for vinyl cyanides, butyl acrylate for acrylic esters and methyl methacrylate for methacrylic esters.

The ratio of the rubbery elastomer to the vinyl compound may be 10/90 to 90/10, and preferably 30/70 to 80/20. If the ratio is less than 10/90, there is a tendency to reduce the impact resistance, while if the ratio is more than 90/10, there is a tendency to insufficient improvement in the impact resistance.

The above-mentioned polyester elastomers are preferably copolymers each comprising an aromatic dicarboxylic acid or an ester-forming derivative thereof, a diol or an ester-forming derivative thereof and a polyether having a number average molecular weight of 700 to 3,000, with the polyether-derived unit accounting for 5 to 70%. When the proportion of the polyether-derived unit is less than 5%, the effect of improving the impact resistance tends to be insignificant, while when the proportion exceeds 70%, the heat resistance tends to be reduced.

The solution viscosity, expressed as the inherent viscosity number (LV) determined at a concentration of 0.5 g/dl in phenol/tetrachloroethane (1:1, w/w) at 25ºC, for the above-mentioned polyester elastomer is preferably 0.3 to 2.0. If the inherent viscosity number is less than 0.3, the impact strength and chemical resistance of the molded parts are insufficient, while if the viscosity number is more than 2.0, the moldability tends to deteriorate.

As specific examples of the dicarboxylic acids or ester-forming derivatives thereof used in the production of the polyester elastomer, terephthalic acid, isophthalic acid and their ester-forming derivatives may be mentioned.

Diols or ester-forming derivatives thereof include ethylene glycol, propylene glycol, tetramethylene glycol and their ester-forming derivatives.

As examples of the polyether, there may be mentioned the ethers listed in JP-A-2-92953, namely, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, ethylene oxide-propylene oxide copolymers, and bisphenol A-modified polyethylene glycol obtainable by reacting ethylene oxide with 2,2-bis(p-hydroxyphenyl)propane (bisphenol A), and the like.

As mentioned above, the number average molecular weight of this polyether is preferably 700 to 3000, and more preferably 800 to 2000. If the molecular weight is less than 700, there is a deterioration in heat resistance, impact resistance and heat distortion temperature. If it is more than 3000, there is a tendency to deteriorate heat stability.

The proportion of the modifier for the impact strength is 0 to 40% and preferably 1 to 20%, based on the sum of (A) to (C). If the proportion exceeds 40%, there will be losses in terms of rigidity and heat distortion temperature.

The halogenated phenoxy resin which represents component (D) according to the invention is a flame-retardant component having repeating structural chain units of the general formula (I)

Although this resin is generally a glycidyl and/or hydroxy terminated resin, these terminal groups may be blocked by a carboxylic acid, a phenol, an amine or an alcohol.

In the above general formula (I), X represents bromine or chlorine and Y represents a C₁₋₁₀alkylene group, an alkylidene group, a carbonyl group, -O-, -S- or -SO₂-.

The halogenated phenoxy resin of the general formula (I) can be prepared, inter alia, by reacting a halogenated bisphenol glycidyl ether with a halogenated bisphenol in the presence of a suitable catalyst, optionally in a solvent.

Examples of the halogenated bisphenol compound include: 2,2-bis-(3,5-dibromo-4-hydroxyphenyl)-propane, bis-(3,5-dibromo-4-hydroxyphenyl)-phenylmethane, 1,1- bis-(3,5-dibromo-4-hydroxyphenyl)-ethane, bis-(3,5-dibromo-4-hydroxyphenyl)-sulfone, bis-(3,5-dibromo-4-hydroxyphenyl)-ether, bis-(3,5-dibromo-4-hydroxyphenyl)-ketone, bis-(3,5-dibromo-4-hydroxyphenyl)-sulfide, 2,2-bis-(3,5-dichloro-4-hydroxyphenyl)-propane, Bis(3,5-dichloro-4-hydroxyphenyl)methane, bis(3,5-dichloro-4-hydroxyphenyl)sulfone, bis(3,5-dichloro-4-hydroxyphenyl)sulfide, and the like. Among these compounds, 2,2- bis(3,5-dibromo-4-hydroxyphenyl)propane, commonly referred to as tetrabromobisphenol A, is preferred in view of its flame-retardant nature.

Furthermore, together with the halogenated bisphenol, usual non-halogenated bisphenol compounds such as 2,2- bis-(4-hydroxyphenyl)-propane, bis-(4-hydroxyphenyl)-sulfone and bis-(4-hydroxyphenyl)-methane can be used in a proportion of not more than 30 mol% based on the total bisphenol compounds.

The weight average molecular weight of the halogenated phenoxy resin is 5,000 to 200,000, preferably 10,000 to 200,000, and more preferably 20,000 to 100,000. If the molecular weight is less than 5,000, there is a tendency for a reduction in stability during molding, bleeding or increased gas evolution. On the other hand, if the weight average molecular weight exceeds the value of 200,000, the flowability during moulding and the mechanical properties of the moulded parts are impaired.

In the composition of the present invention, the proportion of the halogenated phenoxy resin is 3.5 to 30 parts based on 100 parts of components (A), (B) and (C) combined, and preferably 6 to 20 parts on the same basis. If the proportion of this resin is less than 1 part, sufficient flame retardancy may not be obtained, while if the proportion exceeds 50 parts, impact resistance and heat resistance may be deteriorated.

The resin composition according to the invention can contain an antimony compound (component (E)). The antimony compound is an auxiliary agent for flame retardancy. Its use in combination with the halogenated phenoxy resin leads to a synergistic improvement in the flame retardancy.

Examples of the antimony compound usable for this purpose include antimony oxides such as antimony trioxide, antimony pentoxide and the like, antimony phosphate, sodium antimonate and the like.

In the composition according to the invention, the proportion of the antimony compound is 0 to 30 parts and preferably 0.1 to 20 parts, based on 100 parts of components (A), (B) and (C) together. If the proportion exceeds 30 parts, the impact resistance is reduced.

The ratio of components (D) and (E) is not critical, but with regard to the flame retardant property a (D)/(E) ratio of 2/1 to 20/1 (w/w) is preferred.

The resin composition according to the invention can further contain phosphite or phenol stabilizers, light stabilizers, plasticizers, lubricants, mold release agents, UV absorbers, antistatic agents, dyes, pigments and fillers such as glass fibers, talc, mica and the like.

The resin composition of the invention can be prepared by any suitable technique. For example it can be produced by mixing with the aid of a mixer, supermixer or the like or by using a single-screw or multi-screw extruder.

Such mixing may be carried out by mixing components (A), (B), (C) (if used), (D) and (E) (if used) all together in one operation or by mixing some of the ingredients first, adding the remaining ingredients and mixing everything together.

The obtained resin composition of the present invention can be easily molded by known techniques, such as injection molding, extrusion molding, etc., to produce automotive parts, electrical or electronic components, general manufactured articles, etc., which have a flame-retardant nature and are excellent in heat distortion temperature, impact resistance, chemical resistance, and weather resistance.

Thus, the resin composition of the present invention is very satisfactory in moldability and can be molded into various molded articles having excellent properties in impact resistance, heat distortion temperature, flexural modulus, weather resistance and chemical resistance as well as having excellent flame retardant properties.

Detailed description of the preferred embodiments

The following examples and comparative examples serve to further explain the resin composition according to the invention.

Examples 1 to 8 and Comparative Examples 1 to 5

The following dry components (A) to (E) and PEP-36 (product of Adeka-Argus Co.) as a stabilizer were previously mixed in the proportions shown in Table 1. The resulting mixture was pelletized by means of a twin-screw extruder at 270ºC. Using an injection molding machine, the pellets were extruded at 240-280ºC. formed into test pieces. These test pieces were evaluated for various properties. The results are shown in Table 1.

(A) Polycarbonate:

Panlite L-1250 (viscosity average molecular weight approximately 25,000, product of Teijin Kasei Co., Ltd.)

(B) Polyethylene terephthalate resin:

EFG-85A (LV 0.85, product of Kanebo, Ltd.) Formula (I(C) Impact modifier Formula (IC-1: FW-20G (linear low density polyethylene, product of Mitsubishi Kasei Corporation) Formula (IC-2: Core/shell graft polymer prepared by emulsion copolymerization of 40 parts of a rubbery-like elastomer of 67% butyl acrylate and 33% butadiene having an average particle diameter of 0.15 µm, with 60 parts of a mixture of 20% acrylonitrile, 30% methyl methacrylate and 50% styrene.

C-3: Core/shell graft polymer prepared by emulsion copolymerization of 60 parts of a rubbery elastomer of 64% butyl acrylate and 36% butadiene having an average particle diameter of 0.15 µm, with 40 parts of a mixture of 15% acrylonitrile, 30% methyl methacrylate and 55% styrene.

C-4: Thermoplastic polyester elastomer (LV = 0.70) containing 40% of units derived from dimethyl terephthalate and ethylene glycol and 60% of units derived from bisphenol A-modified polyethylene glycol having an average molecular weight of 1000, prepared according to the method described in JP-A-2-92953 (ester exchange in the presence of a catalyst).

(D) Halogenated phenoxy resin:

YPB-43 M (brominated phenoxy resin, weight average molecular weight 60,000, bromine content 53%, product of Tohto Kasei Co., Ltd.)

(E) Antimony compound:

PATOX-C (antimony trioxide, product from The Nihon Mining & Concentrating Co., Ltd.)

Impact resistance

Using notched test pieces of 1/4" thickness, Izod impact strength values were measured in accordance with ASTM D-256.

Temperature resistance

Determined using 1/4" thick test pieces at a load of 4.6 kg/cm2 in accordance with ASTM D-648.

tensile strenght

Determined using an ASTM No. 1 dumbbell in accordance with ASTM D-638.

Elongation at break

Determined according to ASTM No. 1 on a dumbbell as per ASTM D-638.

Bending modulus

Determined using 1/4" thick test pieces in accordance with ASTM D-790.

Flame retardant properties

Evaluated using 1/32" thick test pieces per UL-94.

Appearance of the product

Box-shaped molded parts, each weighing about 100 g, were molded using a 5 ounce injection molding machine at a cylinder temperature of 280ºC and a mold temperature of 70ºC and subjected to overall observation and evaluation according to the following criteria.

o: Homogeneous; no flow marks, silver streaks, burnt spots and ripples.

Δ: Inhomogeneous; flow marks, silver streaks, burns and ripples were observed.

x: Inhomogeneous; significant flow marks, silver streaks, burns and ripples. Table 1

Claims (4)

1. Flame retardant Polyester compositions containing (A) 10 to 90% (wt.%; the same applies to the later statements) of a polycarbonate having an average molecular weight, determined by viscosity, of 10,000 to 60,000, (B) 10 to 90% of a thermoplastic polyester, (C) 0 to 40% of an impact modifier, (D) 3.5 to 30 parts, based on 100 parts (parts by weight, the same applies to later statements) of the combination of (A), (B) and (C), of a halogenated phenoxy resin having a weight average molecular weight of 5,000 to 200,000, which has repeating structural chain units of the general formula (I) wherein X represents a bromine atom or a chlorine atom, Y represents an alkylene group having 1 to 10 carbon atoms, an alkylidene group, a carbonyl group, -O-, -S- or -SO₂-, and (E) 0 to 30 parts, based on 100 parts of the combination of (A), (B) and (C), of an antimony compound. 2. The resin composition according to claim 1, wherein the thermoplastic polyester is polyethylene terephthalate or polytetramethylene terephthalate. 3. The resin composition according to claim 1, wherein the impact modifier is at least one member selected from the group consisting of polyolefins, core/shell graft copolymers and polyester elastomers. 4. The resin composition according to claim 1, wherein the proportion of the antimony compound is 0.1 to 20 parts.