GB2118957A - Polymer composition - Google Patents

Abstract

A polymer composition comprises (I) from 5 to 95 wt.% of a polyester resin having as the acid component terephthalic acid or an ester thereof and as the glycol component from 1 to 25 mole% of a glycol having the formula (I) as given below and from 99 to 75 mole% of tetramethylene glycol, and (II) from 95 to 5 wt.% of a polycarbonate of a di- (monohydroxyphenyl)-substituted aliphatic hydrocarbon. The formula (1) of the glycol is: <IMAGE> in which R1 and R2 are each hydrogen or an alkyl group having 1 to 4 carbon atoms, provided that R1 and R2 are not hydrogen at the same time.

Description

SPECIFICATION Polymer composition This invention relates to a novel polymer composition containing a modified polyester resin.

More specifically, this invention relates to a novel polymer composition with superior properties composed of a modified polyester resin in which the di-(monohydroxyphenyl)-substituted aliphatic hydrocarbon polycarbonate polymer and a portion of tetramethylene glycol constituting polytetramethylene terephthalate has been replaced by a glycol having an alkyl or alkyls in the second position of 1 ,3-propanediol.

The polytetramethylene terephthalate resin (henceforth referred to as PBT resin) is a highly crystalline thermoplastic polyester resin and has a superior affinity toward various fillers and additives.

Due to this property, reinforced PBT resins with added glass fibres, mica, talc, and flame-retarding agents have excellent properties. For example, the said resins are widely used in applications including electrical equipment, electronic parts, and automobile parts. In other words, PBT resins have high mechanical strength, high durability, weather resistance, heat resistance, dimensional stability, and electrical properties. Polytetramethylene terephthalate resins have a higher degree of crystallizdtion compared with polyethylene terephthalate resins and have a higher rate of crystallization. Therefore, the cooling solidification rate is fast and the fluidity is good, making the mouldability of the resin excellent.

Thus, PBT resins are engineering plastics with a good balance between the electrical and mechanical properties, as well as the processing properties.

PBT resins, however, have the following disadvantages.

(1) PBT resins naturally were inferior in dimensional precision when compared with noncrystalline plastics and plastics which are difficult to crystallize. This difference is particularly evident under the influence of a temperature distribution in a metal mold. PBT resins are also subject to a mould shrinkage ratio which is dependent on the thickness of the plastic. When the cooling rate is not constant, the moulded PBT product tends to deform and shrink from the mould, This property accentuates the shrinkage anisotropy of the orientation of the fibre in PBT resins reinforced with glass fibres. The moulded product tends to deform and generate so-called warp.

(2) Unreinforced PBT resins lack plasticity and are sensitive to notching.

In order to improve on these disadvantages, various blended resin compositions have been suggested. Of particular interest is a combination of a PBT resin with a basically noncrystalline resin, polycarbonate resin. In this combination, the glass transition temperature of the polycarbonate is increased to 1500C and the impact resistance is also improved. Based on this result, there are high expectations for the blended materials, and blended compositions with high thermal deformation temperatures and strengths at high temperatures have actually been obtained. However, the improvement in the impact resistance by combining the resin with a polycarbonate was not significant enough and none of the blended materials has satisfied the users' demands as far as the impact resistance is concerned.

Therefore, the inventors have been studying this problem diligently and discovered that a polymer composition with high thermal deformation temperature and strength at high temperatures and with extremely superior impact resistance and rich surface gloss could be obtained by combining a modified polyester resin with a polycarbonate. This invention was completed based on this discovery.

Accordingly, this invention provides a polymer composition comprising (1) a polyester resin containing at least an acid component and a glycol component wherein the acid component is terephthalic acid or an ester thereof and the glycol component is a mixture of 1-25 mole% of a glycol represented by the formula (1) below and 99-75 mole% of tetramethylene glycol and (II) a di (monohydroxyphenyl)-substituted aliphatic hydrocarbon polycarbonate, of which the proportion of (I) is 5-95 wt.% and of (11) is 95-5 wt.%.

The formula (I) of glycol is:

(in which R1 and R2 are hydrogen or an alkyl group with 1-4 carbon atoms and R1 and R2 are not both hydrogen).

The modified PBT resin used in this invention is a polyester resin whose acid component is terephthalic acid and whose glycol component consists of 1-25 moie% of a glycol represented by the general formula (1) above and 99-75 mole% of tetramethylene glycol.

More specific examples of the glycols indicated by the formula (1) are 2-ethyl-2-butyl-1 ,3- propanediol, 2-methyl-2-propyl-1 3-propanediol, 2-methyl-l ,3-propanediol, and 2,2-dimethyl-1,3propanediol. Of these, 2-methyl-1 3-propanediol and 2,2-dimethyl-1 ,3-propanediol (neopentyl glycol) are particularly desirable for use in this invention.

The PBT resin modified according to the description above and used in this invention can be prepared by any of the desired methods listed below.

Basically, the blended product is prepared by mixing all three components 0, O2 and (i) or any two of them, wherein (i) is the resin composition consisting of PBT resin, O2 is a resin composition consisting of a polyester polymer obtained by a polymerization reaction of terephthalic acid and 2 methyl-l ,3-propanediol, and (i) is a resin composition consisting of a polyester copolymer obtained by a polymerization reaction of terephthalic acid and tetramethylene glycol and 2-methyl-1 ,3-propanediol.

In preparing the resin compositions, 0, ), and (i), the conventional process of preparing polyesters can be used without any further modification. In other words, the resin composition can be prepared by the direct method, in which the dicarboxylic acid compound and the diol compound are allowed to polycondensate directly, or by the ester interchange reaction method, in which the polycondensation is allowed to take place through an ester interchange reaction between a lowmolecular-weight alkyl ester compound of a dicarboxylic acid compound and a diol.

As an example, the preparation of a polyester copolymer (ss) from terephthalic acid and tetramethylene glycol and 2-methyl-1 ,3-propanediol is described. One mole of dimethyl terephthalate and an excess of or a total of 1.1 -to-2.0-fold molar excess of a mixed diol of tetramethylene glycol and 2-methyl-i ,3-propanediol are allowed to undergo an esterification-interchange reaction in a stream of nitrogen using a standard esterification catalyst under normal pressure and at a temperature of ca.

1 50--2400C. The methanol produced was distilled and the necessary amount of the catalyst, discolouration inhibitor, and other additives were added. The reaction mixture was allowed to undergo a polycondensation at about 200-2800C under a reduced pressure of less than 5 mm Hg. The catalyst used above refers to a wide range of compounds; examples are titanium compounds such as tetramethoxytita nium, tetraethoxytitanium, tetra-n-propoxytitani u m, tetraisopropoxytitanium, and tetrabutoxytitanium, tin compounds such as di-n-butylin dilaurate, di-n-butylin oxide, and dibutyltin diacetate, and combinations of the acetate salts of magnesium, calcium, or zinc with antimony oxide or the titanium compound listed earlier.These catalysts are used in the range of 0.002-0.8 wt.O/o based on the total copolymer produced. Discolouration inhibitors which are phosphorus-containing compounds such as phosphorous acid, phosphoric acid, trimethyl phosphite, tridecyl phosphite, triphenyl phosphite, trimethyl phosphate, tridecyl phosphate, and triphenyl phosphate are effective. It is preferable to use such a discolouration inhibitor in the range of 0.001--0.3 wt.% base on the total copolymer formed.

The poly-2-substituted-1 ,3-propylene terephthalate component consisting of terephthalic acid and 2-substituted-l ,3-propanediol, a part of the polybutylene terphthalate resin (I) modified according to the invention, amounts to 1 to 25 mole%, preferably 1 to 20 mole%, based on the total polymer (I). If the amount of the poly-2-substituted-1 ,3-propylene terephthalate component is less than 1 mole%, the blend is not improved in respect of plasticity and mould shrinkage. If the amount of the component is larger than 25 mole%, the resulting PBT resin decreases with regard to melting point and crystallization degree whereby there is a reduction in the thermal and mechanical strength.For this reason, the resin is difficult to blend with the polycarbonate (Il) because the resin and the polycarbonate are too different from each other in respect of thermal behaviour.

The modified polyester resin (I) used in this invention is prepared using terephthalic acid, 2substituted-1,3-propanediol, and tetramethylene glycol as starting materials, but it is also possible to use other copolymer components such as polyvalent aliphatic carboxylic acids such as adipic acid, azelaic acid, and sebacic acid, polyvalent aromatic carboxylic acids such as isophthalic acid, trimellitic acid, pyromellitic acid, and 2,6-naphthalene dicarboxylic acid, and polyols such as ethylene glycol, propylene glycol, 1 6-hexanediol, 1 4-dichlorohexanediol, cyclohexane-dimethanol, trimethylolpropane, and pentaerythritol in suitable amount depending on the objectives desired.

Next, the polycarbonate resin (Il) used in this invention is a polycarbonate of di (monohydroxyphenyl)-substituted aliphatic hydrocarbons. More specifically, it is a bisphenol polycarbonate, and 4,4'-dihydroxydiphenylalkane polycarbonate is particularly preferred. The most representative example is the polycarbonate is particularly preferred. The most representative example is the polycarbonate of bisphenol A (4,4'-dihydroxy-2 ,2'-diphenylpropane).

It is desirable that the molecular weight of the polycarbonate (II) be ca. 30,000 or greater than 30,000.

It is acceptable to formulate suitable amounts of the well-known additives in the polymer composition of this invention, depending on the properties and effects desired in the composition. For example, lubricants such as an organic acid amide wax, other crystallization neclei, oxidation inhibitors, ultraviolet ray absorption agents, static electricity inhibitors, and flame-retarding agents can be added.

The polymer composition of this invention can also contain about 5-40 wt.%, or more preferably 10-30 wt% of organic or inorganic fibres or particles as reinforcing fillers. Of the fillers, glass fibre is particularly preferred, and the total weight of the said filler should conform to the range specified above.

Glass fibres have been known to enhance the mechanical properties of the resins and are particularly well known for increasing the impact resistance of polyesters such as PBT resins. The addition of glass fibres to the composition of this invention has an even greater effect than anticipated, and the impact resistance is increased much more than expected. Thus, the amount of the glass fibres added to the polymer composition of this invention can be less than normal and still realize the effect desired.

The composition of this invention consists of 5-95 weight parts, or more preferably 20-80 weight parts of the polycarbonate and 95-5 weight parts, or more preferably 80-20 weight parts of the modified PBT resin. When the amount of the polycarbonate used is less than 5 weight parts, the impact resistance of the blended composition is not improved, and when the said amount exceeds 95 weight parts, the melt flow property of the resin is adversely affected.In preparing the polymer composition of this invention, both components may be mixed at a temperature above the melting point of each polymer; the preferred temperature range is 150--3000C. The blended method can be a chemical method, in which the components are dissolved in a solvent and mixed, or a mechanical method employing rollers, Banbury mixers, extruders, or moulding machines. In either case, the method and equipment which is normally used can be utilized.

Although the reason why a resin composition with an outstanding impact resistance is obtained by this invention is not clearly understood, the following theory has been proposed.

The PBT resins generally have poor impact resistance, since they are resins with high crystallinity.

On the other hand, the polycarbonate resins generally have superior impact resistance, since they are polymers with low degrees of crystallinity. However, a simple blend of a PBT resin and a polycarbonate resin failed to improve the impact resistance as much as expected. This disappointing result was attributed to the fact that the solubility parameter for the PBT resin is 10.8 and that for the polycarbonate resin 9.8. The difference in the solubility parameter of 1.0 and the fact that the PBT resin is a highly crystalline polymer and the polycarbonate resin is relatively noncrystalline were thought to be the cause of poor mutual solubility. That is to say, the blended resin consisting of a PBT resin and a polycarbonate resin contains a PBT phase, a portion in which both resins are mutualiy dissolved in each other, and a polycarbonate phase.These phases exist relatively independently, and this is thought to be the cause of the less-than-expected level of impact resistance.

In contrast to this, the modified PBT resin used in this invention has the glycol component which forms repeating units or a portion of the tetramethylene glycol which is the linear glycol component partially substituted with 2-substituted-l ,3-propanediol, which is a glycol component with a side chain.

The presence of the side chain disrupts the regularity of the polymer chain and correspondingly reduces the degree of crystallinity.

Thus, the modified PBT resin of this invention has a much larger amount of the noncrystalline phase and is thought to give rise to a polymer composition with a surprisingly high impact resistance when mixed well with a polycarbonate resin.

In the following paragraphs, this invention will be explained in more detail with examples, but it is not limited to these examples. In the examples, the term "part" refers to weight parts and the properties of the resins were determined by the following methods.

(1) Content of poly-2-methyl-1 ,3-propylene terephthalate Contents of poly-2-methyl-l ,3-propylene terephthalate as indicated in Table 1 were calculated in terms of mole percent by means of nuclear magnetic resonance spectrum (N MR).

(2) Intrinsic Viscosity The intrinsic viscosity was measured at 250C in o-chlorophenol.

(3) Melting Point and Heat of Fusion The Perkin Elmer DSC-1 B model differential scanning calorimeter was used for this measurement.

The heat of fusion for Sn was used as the standard.

(4) Relative Degree of Crystallinity The peak area based on the fusion of the resin obtained on a differential scanning calorimeter was used. The peak area of PBT (resin 1 in Table 1 below) was given the value of 100%.

(5) Tensile Yield Strength and Tensile Fracture Elongation The Toyo Baldwin Co. Tensilon UTM-1 -5000 B was used according to the method described in ASTM D-638.

(6) Izond Impact Test The Toyo Seiki Seisakushyo Co. Izod Impact Tester was used. For the notched test, the method described in ASTM D-256 was used.

(7) Thermal Deformation Temperature The method described in ASTM D-648 was used under a load of 18.56 kg/cm2.

Synthesis 1 A PBT resin was synthesized according to the method described in the following paragraph.

A mixture of 1 94.0 parts dimethyl terephthalate 135.0 parts tetramethylene glycol, and 0.20 part titanium tetrabutoxide catalyst was placed in a reactor equipped with a double helical ribbon-type agitator. The reaction was allowed to proceed for one hour at 1 800C in a stream of nitrogen under normal pressure. The reaction mixture was then heated for 2.5 hours at 2300 C, and the methanol produced was distilled, yielding 90% of the theoretical amount. Next, 0.02 part of tridecyl phosphite was added to the reaction mixture, and the temperature of the reaction mixture was raised to 2500C.

The pressure within the reaction system was reduced to 0.2 mm Hg over 40 minutes, and the polymerization was allowed to proceed for 3.5 hours under this condition.

Synthesis 2 A modified PBT resin was synthesized according to the method described in the following paragraph.

A mixture of 194.0 parts dimethyl terephthalate, 121.5 parts tetramethylene glycol and 2-methyl1 ,3-propanediol, and 0.20 parts titanium tetrabutozide catalyst was placed in a reactor equipped with a double helical ribbon-type agitator. The reaction was allowed to proceed for one hour at 1 800C in a stream of nitrogen under-normal pressure. The reaction mixture was then heated for 2.5 hours at 2300 C, and 90% of the theoretical amount of methanol produced was distilled. Next, 0.02 part of tridecyl phosphite was added to the reaction mixture, and the temperature of the reaction mixture was raised to 2500 C. The pressure of the reaction system was reduced to 0.2 mm Hg over 40 minutes, and the polymerization was allowed to proceed for 3.5 hours under this condition.

Synthesis 3 and Synthesis 4 Modified PBT resins were synthesized from different proportions of tetramethylene glycol and 2 methyl-l ,3-propanediol as indicated in Table 1 below, using the method described in Synthesis 2.

The properties of the polymers and copolymers obtained in Synthesis 1-4 are tabulated in Table 1 below. Also given below is Table 2, to which reference will be made in the following examples.

TABLE 1

synthesis unit 1 2 3 4 dimethylterephthalate parts 194.0 194.0 194.0 194.0 tetramethylene glycol ,, 135.0 121.5 114.8 87.7 8 2-methyl-113-propanediol ,1 - 13.5 20.2 47.3 tridecyl phosphite ,, 0.02 0.02 0.02 0.02 tetrabutoxytitanium ,, 0; ;20 0.20 0.20 0.20 2-methyl-1,3-propylene terephthalate component % 0 12 18 47 intrinsic viscosity dl/g 0.82 0.72 0.74 0.83 melting point OC 229 213 189 141 relative degree of crystallinity % 100 77 64 8 TABLE 2

a) .

E C > l o I I I 8 9 I re ci P) cn reference LD comparative example unit 1 2 1 2 3 .4 1 2 o t synthesis- m 1 100 g o g 8 X 60 n PBT resin) -K cd O X , , O, O 0r 5, 3 e cw - - - - - - - 60 X . . . ~=~ O yield | kg/cm2 540 670 I 328 '319 t 335 297 ~ fracture elongation 8 87 12.5 19.5 21.0 24.3 1.7 345 v resistance (notched) kg.cmfcm. 2.7 62 4.1 5.4. 6.1 8.3 2.8 15.2 3 5, 44 - did not did not did not did not 40 did not fracture ., -- .. , . ~ o deformation temperature CM 55 I I I I b s o I - I I I O : U O o o o N ot t s & BR< . ~ a3 .&commat; o E aJnix!uí e4s O > Xc ca ao . U! suo!lJOdOJd O O E a EXAMPLES 1,2,3 AND 4 AND COMPARATIVE EXAMPLES 1 AND 2 The polyesters obtained in the synthesis examples and bisphenol A-polycarbonate, available under the tradename "lupilon" from Matsubishi Gas Kagaku Co., Ltd., were air-dried at 600C for 8 hours. The dried polymers were mixed with each other in proportions given in Table 2 above and 0.4 parts of tridecyl phosphite was added to these mixtures.The mixtures were kneaded and extruded into pellets using an extruder equipped with a monoaxial full-flight-type screw whose intemal diameter was 40 mm, maintained at 23 > 250 C. The pellets obtained were air-dried for 8 hours at 80CC and were moulded into test pieces using a standard injection moulding machine at 250"C. The properties of the compositions obtained are tabulated in Table 2 above. The properties of the polycarbonate described above and the polyester (PBT resin) obtained in Synthesis 1 are shown as References 1 and 2.

The purpose of the invention is an improvement of a blend polymer composition of polybutylene glycol and a polycarbonate defined as (II). This is attained by use of the glycol component having 2 alkyl(s)-l ,3-propanediol. The prior blend of polybutylene glycol and the polycarbonate (II), appearing as the comparative example 1, is improved in respect to the thermal deformation temperature and rigidity at a high temperature, compared with polybutylene glycol alone, but is not so improved in the impact resistance as desired. The invention can solve the problem and provide the blend of polybutylene glycol and the polycarbonate (li) with the unexpectedly improved impact resistance, while it is maintained as high in respect of the thermal deformation temperature and the tensile yield strength. It will be understood from the above mentioned data that the invention composition is a blend which has good properties balanced in all respects. Since the blend is required to have a high thermal deformation temperature, the blend of the comparative example 2 having too low a thermal deformation temperature is not suitable.

Claims (8)

1. A polymer composition which comprises (I) from 5 to 95 weight percent of a polyester resin containing at least an acid component and a glycol component, said polyester resin having as the acid component terephthalic acid or an ester thereof and as the glycol component from 1 to 25 mole percent of a glycol having the formula (1) as given below and from 99 to 75 mole percent of tetramethylene glycol; and (II) from 95 to 5 weight percent of a polycarbonate of a di-(monohydroxy-phenyl)substituted aliphatic hydrocarbon: the formula (1) of the glycol being:

in which Ri and R2 are each hydrogen or an alkyl group having 1 to 4 carbon atoms, provided that R and R2 are not hydrogen at the same time.

2. A polymer composition as claimed in claim 1, in which said glycol having the formula (1) is 2 methyl-1 ,3-propylene glycol.

3. A polymer composition as claimed in claim 1 or 2, in which the polyester resin contains the acid component, the glycol component and at least one other component selected from polyvalent aliphatic carboxylic acids, polyvalent aromatic carboxylic acids (other than terephthalic acid) and polyols (other than the glycol component).

4. A polymer composition as claimed in claim 1, 2 or 3, in which the polycarbonate (II) has a molecular weight of at least about 30,000.

5. A polymer composition as claimed in any one of claims 1 to 4, in which the polycarbonate (II) is a bisphenol polycarbonate.

6. A polymer composition as claimed in any one of claims 1 to 5, which alco contains a reinforcing filler in an amount of 5 to 40 weight percent.

7. A polymer composition as claimed in any one of claims 1 to 6, which also contains glass fibre as a reinforcing filler.

8. A polymer composition as claimed in claim 1 and substantially as hereinbefore described with reference to Examples 1 to 4.