NL8200502A - PET moulding compsns. with high resistance to warping - contg. glass fibres and glass flakes - Google Patents

Abstract

Polyethylene terephthalate moulding materials consisting mainly of (a) PET with an inherent viscosity of at least 0.4 dl/g; (b) ca. 20% on mixt. of glass fibres and (c) ca. 10-15wt.% on mixt. of a mixt. of glass flakes. The compsn. may also contain (d) up to 12wt.% on the mixt. of a Na or K salt of an ionic hydrocarbon copolymer of a 2-5C alpha-alkene and a 3-5C alpha,beta-ethylenically unsatd. carboxylic acid in which the COOH gps. are at least partially neutralised with Na(+) or K(+) cations, the copolymer being used in an amt. sufficient to provide a -H H/-H c ratio of less than 0.25 in the mixt., and (e) up to 12wt.% on the mixt. of a low mol. wt. organic cpd. such as esters, ketones, sulphones, sulphoxides, nitriles or amides with at most 30C, in an amt. sufficient to lower the Tpk of the mixt. by at least 4 deg.C. The compsns. give smooth glossy mouldings with good strength and impact resistance in the unnotched state, and which exhibit a low degree of warping.

Description

jr. - i »Β.Ο. 30853 1

Polyethylene terephthalate molding mixture and process for its preparation.

The present invention relates to polyethylene terephthalate (PET) compositions and more particularly to compositions which exhibit low warpage.

It is desirable to obtain polyethylene terephthalate (PET) compositions 5 which are well crystallized and have smooth, glossy surfaces. One method of obtaining such compositions is to use very high molding temperatures, for example above 130 ° C. Another method is to use a crystallization rate enhancing system, as described in British Patent Application No. 2,015,014. This British Patent Application discloses that good quality polyethylene terephthalate articles can be obtained at lower temperatures, for example, 80-100 ° C, when certain materials are added to the resin prior to molding. These additives increase the crystallization rate and molded articles with smooth, glossy surfaces, which are easily removable from molds, are obtained when the materials are used. The additives are 1) a sodium or potassium salt of an ionic hydrocarbon polymer, ie an organic polymer, containing pendant earboxyl groups, and 2) a selected low molecular weight organic compound, such as an ester, ketone, sulfone, sulfoxide, nitrile or amide.

It is desirable to reduce warpage in articles formed from such resins. The warp 25 is generally attributed to the presence of glass fibers in the resin, which are added to improve the strength properties of the PET. Replacement of a dee! of the glass fibers with platelets to reduce warpage is known, as can be seen from British Pat. No. 1,587,894. However, such replacement, especially with mica or talc platelets, generally reduces tensile strength and impact notched strength of articles formed from PET resin.

It is the object of the present invention to provide glass fiber reinforced polyethylene terephthalate molding mixtures which can be molded into articles with a low degree of warpage and with good strength and impact strength in the non-notched condition.

8200502 «fc V, 2

The present invention, in its broadest sense, is a molding mixture containing the following ingredients: a) polyethylene terephthalate, which has an inherent viscosity of at least 0.4 dl / g, 5 b) about 20 wt% of a mixture of glass fibers and c) about 10-15% by weight (> of a mixture of glass slides.

The molding mixture may preferably contain additional ingredients which increase the crystallization rate, such as d) to 12% by weight of the mixture of a sodium or potassium salt of an ionic hydrocarbon polymer of an o-olefin having 2-5 carbon atoms and an o 3-ethylenic unsaturated carboxylic acid with 3-5 carbon atoms, in which the carboxyl groups are at least partly

X X

neutralized with Na or Z cations, provided that the amount of the copolymer present is sufficient to provide a 15 V-Ho ratio of less than 0.25 to the mixture and e) up to 12 wt% of the mixture of a low molecular weight organic compound, ie an ester, ketone, sulfone, sulfoxide, nitrile or amide with no more than 30 carbon atoms, provided that the amount of the compound is sufficient to provide the Tpk of the mixture with at least about 4 ° C.

The polyethylene terephthalate used is a polyethylene terephthalate with an inherent viscosity of at least 0.4 dl / g as measured according to ASTM D-2857. The polyethylene terephthalate 25 preferably has an upper inherent viscosity limit of about 1. 2 dl / g. The inherent viscosity is measured in a mixture of dichloromethane and trifluoroacetic acid in the volume ratio 3s1 "bid 30 ° C. The polyethylene terephthalate may contain up to 10 wt. 90 of a non-polymeric comonomer. Representative monomer comonomers include diethylene glycol , butane-diol, cyclohexane-dimethanol and other diols and glutaric acid and other dicarboxylic acids Non-polymer is understood to mean that the comonomer does not contain more than two repeating units other than -CHg- Preferably the polyethylene terephthalate is present in an amount between 35 and 70% by weight, based on the mixture.

The glass fibers will generally have lengths of 4.8 mm or less, while the glass slides will generally have a thickness between 0.0025 and 0.0076 mm and lengths and widths between 0.025 mm and 3.2 mm.

40 Examples of the sodium or potassium salts of the ionic 8200502 • Λ - * 3 hydrocarbon copolymer (hereinafter ionomer resin) are salts of a βζ-olefin with 2-5 carbon atoms and an o <, fi> -ethenically unsaturated carboxylic acid with 5 -5 carbon atoms, in which the carboxyl groups are at least partially neutralized with Na + or K + cations, 5 salts of olefin copolymers and acrylic or methacrylic acids, or salts of copolymers of aromatic olefins and maleic anhydride. Preferably, these materials include the sodium or potassium salt of ethylene / methacrylic acid eopolymers (including partially or completely neutralized salts, e.g. at least about 30% neutralized), the sodium salt of styrene / maleic anhydride eopolymers (including of both partially and fully neutralized salts, e.g. neutralized at least about 30%) and sodium versatate. In the aforementioned copolymers, the olefin or aromatic olefin moiety usually comprises 50-98% by weight of the copolymer and preferably 80-98% by weight. A particularly preferred material is the sodium salt of ethylene / methacrylic acid copolymer. The eopolymers can be prepared at high pressure by conventional polymerization technology.

Representative of the low molecular weight organic compounds are aromatics or organic ketones, sulfones. sulfoxides, nitriles or amides. Preferably, the organic ester is the product of an aromatic carboxylic acid of 7-11 carbon atoms, which contains at least έέ carboxyl group per aromatics and an alcohol selected from the alcohols of the formula (HOCHg ^ R1, where x 1, 2 or 3 and R * is a hydrocarbon group having 2-15 carbon atoms, preferably 2-10 carbon atoms, or that of the formula H0- (R "O) R" ', wherein y is a major number between 1 and 15 and y preferably between 1 eh 8, R ”is a hydrocarbon group with 2-15 • 30 carbon atoms, preferably 2-8 carbon atoms and R, M is hydrogen or a hydrocarbon group with 2-20 carbon atoms, preferably 2-12 carbon atoms. Preferred are the esters in which the aromatoic carboxylic acid and the aliphatic carboxylic acid are hydrocarbon acids containing 1-3 carboxyl groups and the alcohols are aliphatic In other words, the R groups in the alcohols are alkyl or alkylene depending on the particular R- group also preferably zal When the carboxylic acids contain two or more carboxyl groups, the carboxyl groups all react to form ester (COO) bonds, i.e. there will be no free carboxyl groups in the ester. Preferably 8200502 4, all the hydroxyl groups of the alcohols will also be reacted to form ester (COO) bonds, i.e., there will be no free hydroxyl groups in the ester.

A particularly preferred group of esters are esters in which the acid is benzoic acid and the alcohol in which R 'is alkylene of 4-6 carbon atoms, preferably neopentyl glycol, or is H (R "O) H, wherein R "is ethylene or propylene v and y is 2 or 3.

While the organic esters are preferred for use herein, other compounds which may be used include: 0 tt organic ketones of the formula RCR, organic sulfones of the formula RgSOg, 15 organic sulfoxides of the formula RgSO, organic nitriles with the formula RCR or 0.

II

organic amides of the formula RCMR'R or 0 ft \ 20 RSONR'R, wherein each group R may be equal to or different from any other group R and a hydrocarbon group having 1-25 carbon atoms, while R1 is hydrogen or is a hydrocarbon group of 1-25 carbon atoms.

Preferred zetones, sulfones, sulfoxides, nitriles and amides are those in which the R groups in the formulas given above for these organic compounds are aryl groups of 6-10 carbon atoms or alkyl groups of 1-10 carbon atoms to be.

Specific compounds within these definitions are referred to as 30 vermelds diphenyl carbonate, neopentyl glycol dibenzoate, triethylene glycol dibenzoate, diethyleenglycoldibenzoaat3dipropyleenglycol-dibenzoate, tris-2-ethylhexyl trimellitate, butylcarbitoladipaat, triethylene glycol caprylate, phenyl benzoate, pentaerythritol tetrabenzoate, trimethylol ethane tribenzoate, dioctylphthalate, 35 diisodecylphthalate, benzophenone, 4% flu: hbenzophenone, diphenyl sulfone, R-ethyl-o, p-toluenesulfonamide, totyl sulfoxide, lauryl nitrile and erucyl nitrile.

The ionomeric resin and the low molecular weight organic compound contribute to obtain molded articles having a high surface gloss 8200502 at molding temperatures below 110 ° C by increasing the crystallization rate of polyethylene terephthalate. The ionomeric resin is believed to contribute primarily in increasing the crystallization rate, while the low molecular weight organic compound is believed to be primarily the mobility of the crystallization resin. polyethylene terephthalate in its molten state improves by reducing the viscosity of the polymer blend. Both are necessary to obtain the high gloss found in the articles formed in the composition.

The amount of sun present is an amount which will result in a Hg / Hc injury of the mixture of less than 0.25. To find the _Hg / _Hc, the polyethylene terephthalate 15 is formed at 70 ° C into bars with a thickness of 1.6 mm. The bars are heated at a rate of 10 ° C per minute and at 95 ° C and 120 ° C. ° C an exotherm (called _Hg.) Is registered on a differential scanning calorimeter (BSC) cell connected to a differential thermal analysis (BTA) device according to Bu Pont 20 900 · The bar is heated at 290 ° C, which is above the melting point , and the molten sample is cooled at 10 ° C per minute. Another exotherm between 200 and 225 ° C (called H) is the exotherm that is recorded when the sample is frozen. It has been found that the -V-Ho wound is an effective method of measuring the degree of crystallization.

The Tpk of the blends is the temperature at which the bubble develops fastest during the heating cycle as stated in the previous paragraph. The amount of the low molecular weight compound present in the mixture is an amount which decreases the Tpk of the mixture by at least 4 ° C relative to that of an identical mixture not containing the compound.

The exposure of the sun to the low molecular weight compound will generally be between 2: 1 and 1: 3.

5. Other additives.

In addition to the components discussed above, the blends of the present invention may contain other additives commonly used with polyester resins, such as dyes, antioxidants, other enhancers, ultraviolet light stabilizers and heat stabilizers and the like.

8200502 6

Preparation

The mixtures of the present invention are prepared by mixing the ingredients together by any conventional method of obtaining an intimate mixture. Neither the temperature nor the temperature are critical. For example, the polyethylene terephthalate can be dry blended in any suitable mixer or tumbler with the other ingredients and the mixture can be extruded by melting. The extrusion product can be chopped. Desirably, the builder or filler may initially be omitted and added after the first melt extrusion, and the resulting mixture can then be extruded by melting.

TASTE '

In the tests that follow, the percentages are based on the total mixture unless otherwise indicated.

The properties of the formed test bars were measured according to the following methods:

Tensile strength and elongation were measured on injection molded rods according to ASTM method B638. Test bars were bars of the ASTM-638 type I bars of 3> 2 mm.

Non-notched tensile strength was measured by cutting injection-molded rods measuring 12.7 × 1 × 27 × 0.32 cm to the size as specified for the Izod test in ASTM Method B256, but without notching the bars and otherwise, by carrying out the test 25 according to the Izod method ASTM B256.

The warp was determined by applying a depth micrometer to a film by measuring the lowest to the highest part of the warp.

Example I

A mixture was made from the following ingredients: 18050 grams (45> 7%) of polyethylene terephthalate (PET) polymer, which had an intrinsic viscosity of 0.60 and was dried to less than 0.05% water, 4880 grams (11.8%) of a brominated polystyrene, 35 870 grams (2.1%) sodium antimonate, 1320 grams (3 * 2%) ethylene / methacrylic acid copolymer (weight ratio & 85:15)> 60% sodium neutralized, 1170 grams (2.8%) neopentyl glycol dibenzoate, 285 grams (0.7%) of the epoxy compound formed from Bisphenol A 40 and epichlorohydrin, 8200502 4. ^ 7 4 250 grams (0.690) polyethylene wax, 41 grams (0.1 %) tetrakis / polyethylene (3,5-di-tert-butyl-4-hydroxy-hydrocinnamate] / methane, 8260 grams (20.0%) glass fibers with a diameter of 9.5 µm and an initial length before extrusion of 4.8 mm and 6200 grams (15.0%) 0.4 mm glass chips

The materials were mechanically mixed together and the mixture obtained after mixing was passed through a 5 cm two-stage extruder in which the vacuum opening was held under a reduced pressure of about 88 kPa. The melt, which was at a temperature of about 285 ° C, was passed through a nozzle to give a single strand, which was cooled and chopped.

The bars thus prepared were dried in a vacuum oven at 120 ° C for 18 hours before molding in a 170 gram injection molding machine. The molding conditions were a fast plunger, a forward time of 10 seconds, a mold closure time of 15 seconds, a melting temperature of 295 ° C, and a mold cavity temperature of 120 ° C. In order to evaluate the physical properties, samples with a thickness of 3.2 mm were prepared as required by ASTM tests D-638 and D-256. In order to evaluate the warp, discs with a diameter of 10 cm and a thickness of 0.18 cm were formed at 120 ° C.

For comparison purposes, a mixture was also prepared, identical to the foregoing, containing 30% glass fibers and no glass flakes. The properties for both these materials are given in Table A. The data indicates that the mixture, which contains both fibers and shavings, of the present invention, had physical properties close to the standard 30% glass fiber product but less than one third of warp.

TAPED A

YAN FEATURES WITH GDAS YER STRENGTH MODIFIED

_PODYETHYDENE TEREFTADATES_

1 A

35 20% glass fibers; 30% glass- 15% glass chips fibers

Impact resistance without notch 11 12

Tensile strength, Mpsi 19 22

Elongation,% 2.2 2.1 40 Flexural modulus, MM psi 1.56 1.50

Warpage, mm 0.6 2.25 8200502 8

Yoorbeeld II and compositions

Example II shows other combinations of glass fibers and glass flakes within the scope of the present invention and compares them with combinations of glass fibers and glass flakes outside the scope of the present invention. All these compositions were flame retardant compositions of polyethylene hierefalate, in which all components had substantially the same proportions as in Example I, except with respect to the amounts of glass fibers and glass flakes. The ingredients were mixed as in Example 10. The ingredients in each composition are listed in the following table, which also contains data on the mixture of Example I for comparative purposes.

Ingredient wt%

I B C D E II

15.PET 43.7 43.7 43.7 39.5 35.8 47.2

Brominated Styrene 11.8 11.8 11.8 11.4 10.6 12.8

Sodium antimonate 2.1 2.1 2.1 2.0 1.9 2.2

Ethylene / methacrylic acid copolymer 20 (60% neutralized) 3.2 3.2 3.2 2.9 2.7 3.4

Neopentyl glycol

Dibenzoate. 2.8 2.8 2.8. 2.7 2.4 3.1

Epoxy of Example I 0.7 0.7 0.7 0.8 0.9 0.6

Polyethylene wax 0.6 0.6 0.6 0.6 0.6 0.6 25 Hydroxyhydro- (cinnamate) methane of example I 0.1 0.1 0.1 0.1 0.1 0.1

Glass fiber from example I 20 15 15 20 20 20 30 Glass chip from example I 15 20 20 '20 25 · 10' uses glass plates with a thickness of 3.2 mm

The properties of these compositions are listed in Table B.

8200502 ** '9 κ' TABLE Β

PROPERTIES OF GLASS-FRESH TERETE-MODIFIED POLYETHYLENE TEREETAIATES

Combination-5 theorem Comparison (letter)%,%

Example Glass-Glass-Impact strength curved (number) fibers sohilfers without notch tensile elongation. draw

Control A 30 - 12 22 2.1 2.2'5

Example I 20 15 11 19 2.2 0.60

Control B 15 20 7 17 2.2 0.375 "C 15 20 '7 16 2.1 0.465 15" D 20 20 9 19 1.9 0.375 "E 20 25 8 19 1.8 0.30

Example II 20 10 10 19 2.2 0.75 • 3.2 mm glass chip instead of 0.4 Jam ·

As can be seen, Equations B, C, D, and E all have low warpage compared to Control A, but all have notched Izod values, which are significantly lower than Control A, and Equations B and C have significantly lower tensile strengths. strength values. Only the compositions of Examples I and II show low warp values and both notched impact strength values and tensile strength values approximating those of Control A.

- conclusions - 8200502

Claims (6)

1. Polyethylene terephthalate molding mixture mainly consisting of; a) polyethylene terephthalate, which has an inherent viscosity of teliminate 0.4 dl / g, 5 b) about 20 wt% of a glass fiber blend, and c) about 10-15 wt% of a glass slide mixture. 2. Mixture according to claim 1, characterized in. that the following components are also present d) up to 12% by weight of the mixture of a sodium or potassium salt 10 of an ionic hydrocarbon copolymer of an ot-olefin with 2-5 carbon atoms and an ethylene-unsaturated carbonznnr. of 3-5 carbon atoms, in which the carboxyl groups are at least partially neutralized with Ha or K cations, with the proviso that. the amount of copolymer present is sufficient to provide an _Hg / _Hc ratio of less than 0.25 to the mixture and e) up to 12% by weight of the mixture of a low molecular weight organic compound, ie an ester , ketone, sulfone, sulfoxide, nitrile or amide having up to 30 carbon atoms, with the proviso that the amount of the compound is sufficient to reduce the Tpk of the mixture by at least about 40. Mixture according to conelusion 2, characterized in that component e) is an organic ester. Mixture according to claims 1 to 3 »characterized. that the glass chip content is 15%. 25 5) Process for preparing a polyethylene terephthalate molding mixture, characterized in. mixing the ingredients of the mixture and then extruding the mixture with melting. 6. Process for the production of a molded article, characterized in that a mixture according to conelusion 1 is melted, the molten mixture is placed in a mold and then the mixture is allowed to solidify. 8200502