CA1067239A - Fire retardant polyester compositions - Google Patents
Fire retardant polyester compositionsInfo
- Publication number
- CA1067239A CA1067239A CA248,855A CA248855A CA1067239A CA 1067239 A CA1067239 A CA 1067239A CA 248855 A CA248855 A CA 248855A CA 1067239 A CA1067239 A CA 1067239A
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- CA
- Canada
- Prior art keywords
- weight
- composition
- fire
- mixture
- polyester
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L67/00—Compositions of polyesters obtained by reactions forming a carboxylic ester link in the main chain; Compositions of derivatives of such polymers
- C08L67/02—Polyesters derived from dicarboxylic acids and dihydroxy compounds
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K3/00—Use of inorganic substances as compounding ingredients
- C08K3/18—Oxygen-containing compounds, e.g. metal carbonyls
- C08K3/20—Oxides; Hydroxides
- C08K3/22—Oxides; Hydroxides of metals
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K5/00—Use of organic ingredients
- C08K5/02—Halogenated hydrocarbons
- C08K5/03—Halogenated hydrocarbons aromatic, e.g. C6H5-CH2-Cl
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L27/00—Compositions of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Compositions of derivatives of such polymers
- C08L27/02—Compositions of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Compositions of derivatives of such polymers not modified by chemical after-treatment
- C08L27/12—Compositions of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Compositions of derivatives of such polymers not modified by chemical after-treatment containing fluorine atoms
- C08L27/18—Homopolymers or copolymers or tetrafluoroethene
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- Chemical & Material Sciences (AREA)
- Health & Medical Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Organic Chemistry (AREA)
- Compositions Of Macromolecular Compounds (AREA)
- Processes Of Treating Macromolecular Substances (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE:
A method for the production of thermoplastic polyester compositions comprising mixing a normally flammable thermoplastic polyester, preferably containing at least 80% by weight of repeating units of ethylene terephthalate, tetramethylene terephthalate or ethylene-1:2-diphenoxyethane-4,4'-dicarboxylate units, an effective amount of fire-retardant additives and an aqueous colloidal dispersion of PTFE, subjecting the mixture to conditions under which the polyester becomes molten and removing volatile materials from the melt.
A method for the production of thermoplastic polyester compositions comprising mixing a normally flammable thermoplastic polyester, preferably containing at least 80% by weight of repeating units of ethylene terephthalate, tetramethylene terephthalate or ethylene-1:2-diphenoxyethane-4,4'-dicarboxylate units, an effective amount of fire-retardant additives and an aqueous colloidal dispersion of PTFE, subjecting the mixture to conditions under which the polyester becomes molten and removing volatile materials from the melt.
Description
Pm 27733 This invention relates to fire-retardant thermoplastic polyester compositions and more particularly to compositions based on polyesters in which at least 80~ by weight of the polymerised units are tetramethylene terephthalate units.
The use o~ thermoplastic polyesters such as poly(ethylene terephthalate) and poly(methylene terephthalate) as materials for engineering applications i~ increas~ng rapidly, These applications ~'requently require that the materials used should be self-extinguishing.
In addition to being self-extinguishing the materials should be re~istant to dripping so that any tendency for burning particles to drip and spread the fire risk is reduced as far as possible. A variety of tests are available for assessing the burning per~ormance of such material~ the Underwriters Laboratories Bulletin No. 94 belng particularly suitable as it takes account o~ both flammability and dripping characteristics.
General Eelectric Company~s British patent specifica-tion No. 1 360 121 published on 17th July, 1974 describes glass-filled, fire-retardant thermoplastic polyester compositions in which a polyttetrafluoroethylene) resin, is used to render the compositions non-dripping as assessed by the Underwriters Laboratories Bulletin No 94 using specimens 1/8" thick The specification states that degradation occurs, resulting in a deterioration in .~
~ ._ .
physical properties of the composition if the ingredients of the composition are not thoroughly dried before compounding.
It has now been found that aqueous dispersions of PTFE resins may be compounded with polyesters without any substantial reduction in the physical properties of the polyester. More-over, the amount of PTFE resin in the form of an aqueous col-loidal dispersion form needed to obtain a satisfactory per-~ormance in the Underwriters Laboratories Test may be consi-derably reduced from the preferred range stated in British Patent specification 1,360,121.
Accordingly there is provided a method of producing a thermoplastic polyester composition comprising intimately ~lending a normally flammable thermoplastic polyester, an effective amount of fire-retardant additives and poly(tetra-fluoroethylene) in the form of an aqueous colloidal dispersion, subjecting the mixture to conditions under which the polyester becomes molten and removing volatile materials from the melt.
Using the method of the invention compositions can be produced which exhibit markedly improved resistance to dripping under burning conditions. thus whereas co~mercially available glass-filled thermoplastic polyester compositions containing about 30% glass and sufficient fire-retardant addi-tives to make them self-extinguishing are normally classified as non-dripping when tested on 1/8" thick samples using the Underwriters Laboratories UL94 test the inclusion of 0.1%
by weight of PTFE added in the form of an aqueous dispersion by the method of the invention improves the non-dripping characteristics of the composition so that samples are classi-fied as non-dripping by this standard test when tested at thicknesses as low as 1/32". On the more severe tests such as the CEE 10 test of the International Commission and Rules for the Approval of Electrical Equipment higher levels of aqueous PTFE dispersion are required to give a non-dripping performance but nevertheless this test also demonstrates that lower levels of aqueous PTFE improve the dripping per-formance by comparison with samples not containing the aqueous PTFE.
The blending operation may be carried out in any mixing apparatus in which the temperature of the mixture is raised to melt the polyester and which is provided with agi-tation means for intimately blending the ingredients of the composition.
The ingredients of the composition may be mixed together, for example by tumbling prior to feeding the mixture to the mixing apparatus or the ingredients may be added in turn to the mixing apparatus. A suitable method ! of compoundlng is by use of a single or double screw extruder. The mixture of ingredients may be added to the feed pocket of such an extruder or alternatively the poly-ester, optionally containing any of the ingredients may be fed to the extruder and the remaining ingredients fed to the molten polyester via a pocket situated in a melt zone of the barrel.
The intimately mixed composition in the extruder is normally passed through an exit die to provide laces which may be cooled in water and chopped into granules. Preferably, the extruder should be provided with a port in the barrel of the extruder for removing volatiles from the composition whilst molten. If volatiles such as water are not removed during passage through the extruder they will escape on .
passing through the exit die but the lace is then likely to contain many voids resulting in granules of low bulk density.
The factors governing the selection of a suitable extruder are well known to those familiar with thermoplastics com-pounding but basically should be chosen to give intimate mixing without a substantial risk of degradation through excessive mechanical shear and overheating. It is an advan-tage of the method of the invention that the aqueous dis-persions of PTFE may be much more easily dispersed than the solid PTFE resins used in British Patent Specification 1,360,121 so that the choice of apparatus for intimately blending the ingredients is much less critical.
The aqueous dispersion of PTFE may be produced by the methods known in the art for polymerising the gaseous tetrafluoroethylene monomer in an aqueous medium containing water soluble free radical catalysts and a surfactant to maintain the polymerised tetrafluoroethylene as a colloidal dispersion. Methods of preparing such dispersions are described in Du Pont's British Patent Specification No. 689,400 published on 25th March, 1953, and our own British Specicication No.
821,353 published on 7th October, 1956. The polymerised dis-persions may contain up to about 40% by weight of polymer.
The surfactant used should be one which does not inhibit or seriously retard the polymerisation and is preferably a fully fluorinated surfactant such as a fully fluorinated car-boxylic or sulphonic acid containing about 6 to 10 carbon atoms. The dispersions obtained from the polymerisation process are not very stable to mechanical shear in the pre-sence of air and may be further stabilised by the addition of additional surfactants. This additional stabilisation may be effected by the use of the conventional stabilisers, par-ticularly the non-ionic surfactants based on ethylene oxide condensates. The conventional stabilisers are very much cheaper than the fluorinated materials. The post-stabilised forms of dispersions may be concentrated by electrodecantation or evaporation to give dispersions containing up to about 65%
of polymer. The ex-autoclave dispersions, post-stabilised dispersions and concentrated dispersions are commercially available. For example, the concentrated dispersion 'Fluon'*
GPI is available from Imperial Chemical Industries Limited.
An unstabilised ex-autoclave variant 'Teflon'* 42 is available from DuPont.
The polyesters suitable for use in the invention are linear thermoplastic polyesters derived from saturated aromatic dicarboxylic acids or their derivatives, such as-terephthalic acid or 1,2-bis(4-carboxyphenoxy)ethane, and dihydric alcohols containing from 2 to 10 carbon atoms such as ethylene glycol, 1,3-propanediol and 1,4-butanediol. The polyesters may con-tain more than one dicarboxylic acid or dihydric alcohol.
Preferred polyesters for moulding applications are those con-taining at least 80% by weight of repeating units selected from ethylene terephthalate, tetramethylene terephthalate or ethylene-1:2-diphenoxyethane-4,4'-dicarboxylate units.
Mixtures of polyesters may usefully be employed.
The fire retardant materials suitable for imparting non-burning characteristics to the compositions may be chosen from a wide variety of compounds which derive their effectiveness from the presence of a substantial proportion of elements such as halogen and phosphorus in the compound.
Halogen-containing organic compounds are particularly effective with polyesters, especially those compounds containing sub-stantial proportions of bromine. Preferred compounds are those of the formula Brm ~ Xn ~ Brp where X may be -O-, -S-, -SO-, -SO2- and -CH2-, n may be 0 or 1 and each of m and p may be from 1 to 5.
The ire retardant additive will normally be effective at a concentration between 3 and 25% by weight of the polyester although the preferred range is 5 to 15%.
When the fire retardant used is a halogenated material its efficiency can be improved by the addition of the Group Vb metal oxides, arsenic, antimony and bismuth oxides, particularly antimony oxide. These are normally included at concentrations of 2% to 10% by weight of the polyester. It is preferred that the weight ratio of halogen to Group Vb metal should be between 0.5:1 to 4:1.
Some fire retardant systems may have a degradative effect on the polyester of the invention during compounding and subsequent processing and it is advisable to evaluate each fire retardant system chosen in the composition of the invention to make sure that the level of degradation is acceptable.
A particularly useful range of compositions may be produced by the inclusion of a variety of reinforcing agents at concentrations from 2 to 80~, preferably 5 to 60 by weight of the total composition.
By "reinforcing agent" is meant any material which will increase the tensile strength of articles formed from compositions containing the agent. Tensile strength is conveniently assessed by the method of ASTM D 638-58T using a pulling rate of 25 mm/min. Typical reinforcing agents are fibrous materials such as glass-fibre, asbestos, carbon fibre and textile fibres.
The most useful of these because of their effective-ness, cheapness and low toxicity are glass fibres. A very large number of types of glass fibre are commercially available but these differ appreciably on their effectiveness when used in a particular thermoplastic and where a high level of tensile strength and other physical properties is an important requirement the glass type should be chosen which is suitable for use with the polyester of the composition. The difference in behaviour is normally attributable to the size used for treating the glass. The suitability of a particular type of glass may be determined by simple evaluation of test pieces of the composition or by seeking guidance from the glass fibre manufacturer.
Glass fibres are commercially available in a variety of forms including continuous roving, and chopped strand normally having average lengths of about 3 to 12 mm. The most suitable form for use in the invention is chopped strand because this can be readily tumbled with the other ingre-dients of the composition, separately metered to the extruder feed pocket, or fed to the molten polyester via entry pockets along the length of the extruder.
The compositions of the invention may contain a variety of other fillers, which are not normally regarded as reinforcing fillers, for the purpose of conferring various other desirable properties on the composition. For example, talc, mica and ballotini may be added in concentrations of about 5 to 50% by weight of the compositions for the purpose of improving the dimensional stability of articles made from the composition, particularly at elevated temperatures.
A variety of additives may be used for improving the electrical performance of the compositions. In particular, the arc and track resistance may be improved by the inclu-sion of wollastonite, talc, various clays and hydrated alumi-nium oxide. These materials are normally included at concen-trations of 5 to 60% by weight of the composition.
Other auxiliary materials such as thermal and ultra-violet stabilisers, lubricants for easier processing, nucleants, and mould release agents may also be included.
The compositions of the invention are suitable for use in a wide variety of engineering applications, par-ticularly where the electrical properties of polyesters may be made use of.
The invention is further illustrated by the following examples.
Example 1 3 kg lots of poly(tetramethylene terephthalate) chip (having an intrinsic viscosity of 0.95 as measured at 25C in a 1% by weight solution of o-chlorophenol) were blended with various proportions of PTFE aqueous dispersion in the proportions tabulated below by tumbling the chip with the dispersion in an end-over-end tumbler for 5 minutes.
490 g of decabromo diphenyl oxide and 175 g of antimony oxide were then added and the tumbling continued for a further 5 minutes. The PTFE dispersion contained 62% by weight of PTFE having a number average particle size of about 0.2 micron. The dispersion had been prepared by polymerisation in the presence of 0.03% (based on the aqueous phase) of the ammonium salt of perfluoro octanoic acid. After poly-merisation to a solids content of 18~ the dispersion was first stabilised with an ethoxylate of an alkyl phenol, sold under the trade mark "Triton" X100, and concentrated by electrodecantation to a solids content of about 65%. The final dispersion had a "Triton" X100 concentration of 2 by weight of the PTFE in the dispersion.
The tumble-blended mixture was fed to a 1 1/2"
vented screw extruder having a length to diameter ratio of 28:1 and the screw having a primary screw volume compression ration of 3:1. The extruder barrel was maintained at a temperature of about 240C. The mixture was extruded as a lace which had no significant porosity. The lace was cooled in water before being chopped into granules. The granules had a moisture content of 0.06%. The extrusion behaviour and melt flow index of each mixture is noted in the table below.
Pm 27733 ~067239 ~he granules were moulded on a St~bbe injection moulding machi~e into test ~amples h~ving a thicknes~ of 1/16~.
~he ~amples were tested according to both the UI94 test and according to the more severe te~t described on page 23 of Sect~on ~ of ~ublication 10i(0ctober 1972) Part 2 of the International Commissio~ and Rules for the Approval of Electrical Equipme~t (CEE 10).
~his te~t which i8 normall~ used for testing electrical components involveQ the application of a butane fl~me to the test Qamples for successive periods of 1 minute, 1 minute and 2 minute~. In the re~ults below the time periods quoted in the aEE 10 are the cumulative times .. ... ` r taken from th~ start of theifirst i~nition.
_ ~/
~067239 ._ . . .. . ~_ _ ~ ~0 = ~ ~ h 'O ~ ~ h ~D ~ C) ~
~) ~ J~ ~~1 ~ O
O ~ ~1 Ul ~1 u~ ~1 u~ ~ 4-1 41 0 ~1 h O ~ 0 rd _ O) ~, ~ O ~ O ~ ~0 ~ ~O ~ ~5 0 tn o ~ ~ O ~ ~ O O ~ O O~ O O~ O O ~ O O
C~ ~ rl ~ O ~ o ~ 0 O ~ ~ oS~ ~ O
_ , _ , , ~
- ~ ~~
~l ~ ~
p ~ ~o ~ - ~
x H Q O
O ~O lQ
~1 ~ 0 0 ~4 ~
~: ~ ~
_ . _ , . E~
S U~ ~ ~D
~ CO
q p, QD7 C~ E~ ~`
,~ ~ S ~ ~ _l ~ O C4 ~ R '~:1 s ,~ 8 ~ s m .o ~ ~ x ~ ~ s ~
~ ~ g~ ~:
w g ~ ~ z ~ x ~o . .. . ..
o~o.~l ~ r ~rc ~ ~
~.~1 a~ ~D ~r N ~1 a~
Ul-rl U~ ~ h 0 a~ o co ~r o o o o o o 3~ 0 ~,~0 ~
~0 67 Z 39 Pm 2773~
~he compositions gave a Y0 performance on the UI94 te~t and were non-drippi~g down to co~centration~
of 0.1~ by weight of P~FE as polymer. ~he behaviour on the more ~evere CEE10 test varied depending on the concentration of P~FE although drippi~g occurred at all concentrations up to 0.8% P~FE.
Co~parative Example A
The procedure of Example ~ wa~ repeated using 0.8% by weight of the composition of a powder form of PIF~ ~old by Imperial Chemical Industrie~ Limited as '~luon' CD1 to replace the aqueous dispersion. During the extrusion of the mixture the extruded lace broke frequently and undispersed PTFE was observed in the lace. The extruded product wa~ moulded i~to teet pieces ~/16" thick a~ in Example 1. Undisporsed 'Fluon' was ~till visible in the moulding~. ~he Rample was found to be no~-dripping and have a V0 rating on the UI94 te~t, but dripped on the fir~t ignition o~
the CEE10 te~t.
Example 2 The procedure of Example 1 wa~ repeated except in that the compo~itio~ fed to the extruder contained 30% b~ weight of chopped strand glass fibre havi~g an average length of 6mm. ~he result~ of testing moulding~
prepared as in Example 1 ~re recorded i~ qable 2.
Pm 27733 _ ~D o ~ .~ p, P~
o ~o.,, b d~ rl tq G~ ~ m~
~ . ~ ~ P, ...
~ D O ~ O ~ O ~
~ ~ ~ o ~o _ .
~1 H O 0~ ~-~; cr~ J
~ ~ _ ~ ~ o~ o a E~ h H ~ D 1~
_ __ ~rl~ ~ C'
The use o~ thermoplastic polyesters such as poly(ethylene terephthalate) and poly(methylene terephthalate) as materials for engineering applications i~ increas~ng rapidly, These applications ~'requently require that the materials used should be self-extinguishing.
In addition to being self-extinguishing the materials should be re~istant to dripping so that any tendency for burning particles to drip and spread the fire risk is reduced as far as possible. A variety of tests are available for assessing the burning per~ormance of such material~ the Underwriters Laboratories Bulletin No. 94 belng particularly suitable as it takes account o~ both flammability and dripping characteristics.
General Eelectric Company~s British patent specifica-tion No. 1 360 121 published on 17th July, 1974 describes glass-filled, fire-retardant thermoplastic polyester compositions in which a polyttetrafluoroethylene) resin, is used to render the compositions non-dripping as assessed by the Underwriters Laboratories Bulletin No 94 using specimens 1/8" thick The specification states that degradation occurs, resulting in a deterioration in .~
~ ._ .
physical properties of the composition if the ingredients of the composition are not thoroughly dried before compounding.
It has now been found that aqueous dispersions of PTFE resins may be compounded with polyesters without any substantial reduction in the physical properties of the polyester. More-over, the amount of PTFE resin in the form of an aqueous col-loidal dispersion form needed to obtain a satisfactory per-~ormance in the Underwriters Laboratories Test may be consi-derably reduced from the preferred range stated in British Patent specification 1,360,121.
Accordingly there is provided a method of producing a thermoplastic polyester composition comprising intimately ~lending a normally flammable thermoplastic polyester, an effective amount of fire-retardant additives and poly(tetra-fluoroethylene) in the form of an aqueous colloidal dispersion, subjecting the mixture to conditions under which the polyester becomes molten and removing volatile materials from the melt.
Using the method of the invention compositions can be produced which exhibit markedly improved resistance to dripping under burning conditions. thus whereas co~mercially available glass-filled thermoplastic polyester compositions containing about 30% glass and sufficient fire-retardant addi-tives to make them self-extinguishing are normally classified as non-dripping when tested on 1/8" thick samples using the Underwriters Laboratories UL94 test the inclusion of 0.1%
by weight of PTFE added in the form of an aqueous dispersion by the method of the invention improves the non-dripping characteristics of the composition so that samples are classi-fied as non-dripping by this standard test when tested at thicknesses as low as 1/32". On the more severe tests such as the CEE 10 test of the International Commission and Rules for the Approval of Electrical Equipment higher levels of aqueous PTFE dispersion are required to give a non-dripping performance but nevertheless this test also demonstrates that lower levels of aqueous PTFE improve the dripping per-formance by comparison with samples not containing the aqueous PTFE.
The blending operation may be carried out in any mixing apparatus in which the temperature of the mixture is raised to melt the polyester and which is provided with agi-tation means for intimately blending the ingredients of the composition.
The ingredients of the composition may be mixed together, for example by tumbling prior to feeding the mixture to the mixing apparatus or the ingredients may be added in turn to the mixing apparatus. A suitable method ! of compoundlng is by use of a single or double screw extruder. The mixture of ingredients may be added to the feed pocket of such an extruder or alternatively the poly-ester, optionally containing any of the ingredients may be fed to the extruder and the remaining ingredients fed to the molten polyester via a pocket situated in a melt zone of the barrel.
The intimately mixed composition in the extruder is normally passed through an exit die to provide laces which may be cooled in water and chopped into granules. Preferably, the extruder should be provided with a port in the barrel of the extruder for removing volatiles from the composition whilst molten. If volatiles such as water are not removed during passage through the extruder they will escape on .
passing through the exit die but the lace is then likely to contain many voids resulting in granules of low bulk density.
The factors governing the selection of a suitable extruder are well known to those familiar with thermoplastics com-pounding but basically should be chosen to give intimate mixing without a substantial risk of degradation through excessive mechanical shear and overheating. It is an advan-tage of the method of the invention that the aqueous dis-persions of PTFE may be much more easily dispersed than the solid PTFE resins used in British Patent Specification 1,360,121 so that the choice of apparatus for intimately blending the ingredients is much less critical.
The aqueous dispersion of PTFE may be produced by the methods known in the art for polymerising the gaseous tetrafluoroethylene monomer in an aqueous medium containing water soluble free radical catalysts and a surfactant to maintain the polymerised tetrafluoroethylene as a colloidal dispersion. Methods of preparing such dispersions are described in Du Pont's British Patent Specification No. 689,400 published on 25th March, 1953, and our own British Specicication No.
821,353 published on 7th October, 1956. The polymerised dis-persions may contain up to about 40% by weight of polymer.
The surfactant used should be one which does not inhibit or seriously retard the polymerisation and is preferably a fully fluorinated surfactant such as a fully fluorinated car-boxylic or sulphonic acid containing about 6 to 10 carbon atoms. The dispersions obtained from the polymerisation process are not very stable to mechanical shear in the pre-sence of air and may be further stabilised by the addition of additional surfactants. This additional stabilisation may be effected by the use of the conventional stabilisers, par-ticularly the non-ionic surfactants based on ethylene oxide condensates. The conventional stabilisers are very much cheaper than the fluorinated materials. The post-stabilised forms of dispersions may be concentrated by electrodecantation or evaporation to give dispersions containing up to about 65%
of polymer. The ex-autoclave dispersions, post-stabilised dispersions and concentrated dispersions are commercially available. For example, the concentrated dispersion 'Fluon'*
GPI is available from Imperial Chemical Industries Limited.
An unstabilised ex-autoclave variant 'Teflon'* 42 is available from DuPont.
The polyesters suitable for use in the invention are linear thermoplastic polyesters derived from saturated aromatic dicarboxylic acids or their derivatives, such as-terephthalic acid or 1,2-bis(4-carboxyphenoxy)ethane, and dihydric alcohols containing from 2 to 10 carbon atoms such as ethylene glycol, 1,3-propanediol and 1,4-butanediol. The polyesters may con-tain more than one dicarboxylic acid or dihydric alcohol.
Preferred polyesters for moulding applications are those con-taining at least 80% by weight of repeating units selected from ethylene terephthalate, tetramethylene terephthalate or ethylene-1:2-diphenoxyethane-4,4'-dicarboxylate units.
Mixtures of polyesters may usefully be employed.
The fire retardant materials suitable for imparting non-burning characteristics to the compositions may be chosen from a wide variety of compounds which derive their effectiveness from the presence of a substantial proportion of elements such as halogen and phosphorus in the compound.
Halogen-containing organic compounds are particularly effective with polyesters, especially those compounds containing sub-stantial proportions of bromine. Preferred compounds are those of the formula Brm ~ Xn ~ Brp where X may be -O-, -S-, -SO-, -SO2- and -CH2-, n may be 0 or 1 and each of m and p may be from 1 to 5.
The ire retardant additive will normally be effective at a concentration between 3 and 25% by weight of the polyester although the preferred range is 5 to 15%.
When the fire retardant used is a halogenated material its efficiency can be improved by the addition of the Group Vb metal oxides, arsenic, antimony and bismuth oxides, particularly antimony oxide. These are normally included at concentrations of 2% to 10% by weight of the polyester. It is preferred that the weight ratio of halogen to Group Vb metal should be between 0.5:1 to 4:1.
Some fire retardant systems may have a degradative effect on the polyester of the invention during compounding and subsequent processing and it is advisable to evaluate each fire retardant system chosen in the composition of the invention to make sure that the level of degradation is acceptable.
A particularly useful range of compositions may be produced by the inclusion of a variety of reinforcing agents at concentrations from 2 to 80~, preferably 5 to 60 by weight of the total composition.
By "reinforcing agent" is meant any material which will increase the tensile strength of articles formed from compositions containing the agent. Tensile strength is conveniently assessed by the method of ASTM D 638-58T using a pulling rate of 25 mm/min. Typical reinforcing agents are fibrous materials such as glass-fibre, asbestos, carbon fibre and textile fibres.
The most useful of these because of their effective-ness, cheapness and low toxicity are glass fibres. A very large number of types of glass fibre are commercially available but these differ appreciably on their effectiveness when used in a particular thermoplastic and where a high level of tensile strength and other physical properties is an important requirement the glass type should be chosen which is suitable for use with the polyester of the composition. The difference in behaviour is normally attributable to the size used for treating the glass. The suitability of a particular type of glass may be determined by simple evaluation of test pieces of the composition or by seeking guidance from the glass fibre manufacturer.
Glass fibres are commercially available in a variety of forms including continuous roving, and chopped strand normally having average lengths of about 3 to 12 mm. The most suitable form for use in the invention is chopped strand because this can be readily tumbled with the other ingre-dients of the composition, separately metered to the extruder feed pocket, or fed to the molten polyester via entry pockets along the length of the extruder.
The compositions of the invention may contain a variety of other fillers, which are not normally regarded as reinforcing fillers, for the purpose of conferring various other desirable properties on the composition. For example, talc, mica and ballotini may be added in concentrations of about 5 to 50% by weight of the compositions for the purpose of improving the dimensional stability of articles made from the composition, particularly at elevated temperatures.
A variety of additives may be used for improving the electrical performance of the compositions. In particular, the arc and track resistance may be improved by the inclu-sion of wollastonite, talc, various clays and hydrated alumi-nium oxide. These materials are normally included at concen-trations of 5 to 60% by weight of the composition.
Other auxiliary materials such as thermal and ultra-violet stabilisers, lubricants for easier processing, nucleants, and mould release agents may also be included.
The compositions of the invention are suitable for use in a wide variety of engineering applications, par-ticularly where the electrical properties of polyesters may be made use of.
The invention is further illustrated by the following examples.
Example 1 3 kg lots of poly(tetramethylene terephthalate) chip (having an intrinsic viscosity of 0.95 as measured at 25C in a 1% by weight solution of o-chlorophenol) were blended with various proportions of PTFE aqueous dispersion in the proportions tabulated below by tumbling the chip with the dispersion in an end-over-end tumbler for 5 minutes.
490 g of decabromo diphenyl oxide and 175 g of antimony oxide were then added and the tumbling continued for a further 5 minutes. The PTFE dispersion contained 62% by weight of PTFE having a number average particle size of about 0.2 micron. The dispersion had been prepared by polymerisation in the presence of 0.03% (based on the aqueous phase) of the ammonium salt of perfluoro octanoic acid. After poly-merisation to a solids content of 18~ the dispersion was first stabilised with an ethoxylate of an alkyl phenol, sold under the trade mark "Triton" X100, and concentrated by electrodecantation to a solids content of about 65%. The final dispersion had a "Triton" X100 concentration of 2 by weight of the PTFE in the dispersion.
The tumble-blended mixture was fed to a 1 1/2"
vented screw extruder having a length to diameter ratio of 28:1 and the screw having a primary screw volume compression ration of 3:1. The extruder barrel was maintained at a temperature of about 240C. The mixture was extruded as a lace which had no significant porosity. The lace was cooled in water before being chopped into granules. The granules had a moisture content of 0.06%. The extrusion behaviour and melt flow index of each mixture is noted in the table below.
Pm 27733 ~067239 ~he granules were moulded on a St~bbe injection moulding machi~e into test ~amples h~ving a thicknes~ of 1/16~.
~he ~amples were tested according to both the UI94 test and according to the more severe te~t described on page 23 of Sect~on ~ of ~ublication 10i(0ctober 1972) Part 2 of the International Commissio~ and Rules for the Approval of Electrical Equipme~t (CEE 10).
~his te~t which i8 normall~ used for testing electrical components involveQ the application of a butane fl~me to the test Qamples for successive periods of 1 minute, 1 minute and 2 minute~. In the re~ults below the time periods quoted in the aEE 10 are the cumulative times .. ... ` r taken from th~ start of theifirst i~nition.
_ ~/
~067239 ._ . . .. . ~_ _ ~ ~0 = ~ ~ h 'O ~ ~ h ~D ~ C) ~
~) ~ J~ ~~1 ~ O
O ~ ~1 Ul ~1 u~ ~1 u~ ~ 4-1 41 0 ~1 h O ~ 0 rd _ O) ~, ~ O ~ O ~ ~0 ~ ~O ~ ~5 0 tn o ~ ~ O ~ ~ O O ~ O O~ O O~ O O ~ O O
C~ ~ rl ~ O ~ o ~ 0 O ~ ~ oS~ ~ O
_ , _ , , ~
- ~ ~~
~l ~ ~
p ~ ~o ~ - ~
x H Q O
O ~O lQ
~1 ~ 0 0 ~4 ~
~: ~ ~
_ . _ , . E~
S U~ ~ ~D
~ CO
q p, QD7 C~ E~ ~`
,~ ~ S ~ ~ _l ~ O C4 ~ R '~:1 s ,~ 8 ~ s m .o ~ ~ x ~ ~ s ~
~ ~ g~ ~:
w g ~ ~ z ~ x ~o . .. . ..
o~o.~l ~ r ~rc ~ ~
~.~1 a~ ~D ~r N ~1 a~
Ul-rl U~ ~ h 0 a~ o co ~r o o o o o o 3~ 0 ~,~0 ~
~0 67 Z 39 Pm 2773~
~he compositions gave a Y0 performance on the UI94 te~t and were non-drippi~g down to co~centration~
of 0.1~ by weight of P~FE as polymer. ~he behaviour on the more ~evere CEE10 test varied depending on the concentration of P~FE although drippi~g occurred at all concentrations up to 0.8% P~FE.
Co~parative Example A
The procedure of Example ~ wa~ repeated using 0.8% by weight of the composition of a powder form of PIF~ ~old by Imperial Chemical Industrie~ Limited as '~luon' CD1 to replace the aqueous dispersion. During the extrusion of the mixture the extruded lace broke frequently and undispersed PTFE was observed in the lace. The extruded product wa~ moulded i~to teet pieces ~/16" thick a~ in Example 1. Undisporsed 'Fluon' was ~till visible in the moulding~. ~he Rample was found to be no~-dripping and have a V0 rating on the UI94 te~t, but dripped on the fir~t ignition o~
the CEE10 te~t.
Example 2 The procedure of Example 1 wa~ repeated except in that the compo~itio~ fed to the extruder contained 30% b~ weight of chopped strand glass fibre havi~g an average length of 6mm. ~he result~ of testing moulding~
prepared as in Example 1 ~re recorded i~ qable 2.
Pm 27733 _ ~D o ~ .~ p, P~
o ~o.,, b d~ rl tq G~ ~ m~
~ . ~ ~ P, ...
~ D O ~ O ~ O ~
~ ~ ~ o ~o _ .
~1 H O 0~ ~-~; cr~ J
~ ~ _ ~ ~ o~ o a E~ h H ~ D 1~
_ __ ~rl~ ~ C'
2~
e~4~
~ .
~00 ~'3('0 O O
1~
e~4~
~ .
~00 ~'3('0 O O
1~
Claims (11)
1. A method of producing a thermoplastic polyester composition comprising mixing a normally flammable thermoplastic polyester derived from saturated aromatic dicarboxylic acids and dihydric alcohols containing from 2 to 10 carbon atoms, an effective amount of fire-retardant additives and polytetra-fluoroethylene in the form of an aqueous colloidal dispersion, subjecting the mixture to conditions under which the polyester becomes molten and removing volatile materials from the melt, so that there is produced a composition which has a rating of 94 VO according to underwriter's laboratory's test standard UL 94 when measured on a sample of 1/16 inch thickness and which is non-dripping.
2. A method according to Claim 1 in which the dis-persion has been stabilised after polymerisation with a non-ionic surfactant.
3. A method according to Claim 1 in which the con-centration of poly(tetrafluoroethylene) solids used by weight of the total composition is between 0.1 and 8.0%.
4. A method according to Claim 3 in which the con-centration of fire-retardant additive is between 3 and 25% by weight of the total composition.
5. A method according to Claim 4 in which the fire-retardant additive comprises a mixture of a halogenated fire-retardant and a Group Vb metal oxide.
6. A method according to Claim 1 in which the mixture includes from 2 to 80% by weight of a reinforcing filler.
7. A method according to Claim 6 in which the re-inforcing filler is glass fibre, asbestos, carbon fibre or textile fibres.
8. A method according to Claim 1 in which from 5 to 50% by weight of the composition of a filler selected from talc, mica, ballotini, wollastonite, clays and hydrated aluminium oxide is added.
9. A method according to Claim 8 in which the con-centration of poly(tetrafluoroethylene) solids is from 0.1 to 1.0% by weight of the composition.
10. A method according to Claim 1 in which at least 80% by weight of the repeating units of the polyester are ethylene terephthalate, tetramethylene terephthalate, or ethylene-1:2-diphenoxyethylene-4,4'-dicarboxylate units.
11. A method according to Claim 1 in which the mixture is free of reinforcing filler.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB14792/75A GB1543557A (en) | 1975-04-10 | 1975-04-10 | Fire-retardant polyester compositions |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1067239A true CA1067239A (en) | 1979-11-27 |
Family
ID=10047568
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA248,855A Expired CA1067239A (en) | 1975-04-10 | 1976-03-25 | Fire retardant polyester compositions |
Country Status (10)
| Country | Link |
|---|---|
| JP (1) | JPS51127150A (en) |
| CA (1) | CA1067239A (en) |
| DE (1) | DE2615071A1 (en) |
| ES (1) | ES446861A1 (en) |
| FR (1) | FR2307014A1 (en) |
| GB (1) | GB1543557A (en) |
| IT (1) | IT1062067B (en) |
| NL (1) | NL7603771A (en) |
| SE (1) | SE419095B (en) |
| ZA (1) | ZA761699B (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| NL7907435A (en) * | 1979-10-08 | 1981-04-10 | Akzo Nv | Polyethylene terephthalate molding material with reduced flammability, and molded parts therefrom. |
| CA1174780A (en) * | 1980-08-06 | 1984-09-18 | John Christiansen | High gloss polyethylene terephthalate reinforced resin compositions |
| DE3713747A1 (en) * | 1987-04-24 | 1988-11-17 | Basf Ag | FLAME RETARDED THERMOPLASTIC POLYESTER MOLDING |
| DE3733840A1 (en) * | 1987-10-07 | 1989-04-20 | Basf Ag | GLASS FIBER REINFORCED FLAME PROTECTED THERMOPLASTIC MOLDING MATERIALS BASED ON POLYESTERS AND GRAFT POLYMERS |
| JP2846336B2 (en) * | 1989-04-07 | 1999-01-13 | ポリプラスチックス株式会社 | Flame-retardant polyester resin composition and preparation method thereof |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3723373A (en) * | 1971-10-04 | 1973-03-27 | American Cyanamid Co | 0.1% to about 2.0% by weight polytetrafluoroethylene emulsion modified polyethylene terephthalate with improved processing characteristics |
-
1975
- 1975-04-10 GB GB14792/75A patent/GB1543557A/en not_active Expired
-
1976
- 1976-03-19 ZA ZA761699A patent/ZA761699B/en unknown
- 1976-03-25 CA CA248,855A patent/CA1067239A/en not_active Expired
- 1976-03-31 IT IT21782/76A patent/IT1062067B/en active
- 1976-04-05 FR FR7609820A patent/FR2307014A1/en active Granted
- 1976-04-07 SE SE7604081A patent/SE419095B/en unknown
- 1976-04-07 DE DE19762615071 patent/DE2615071A1/en not_active Withdrawn
- 1976-04-09 ES ES446861A patent/ES446861A1/en not_active Expired
- 1976-04-09 NL NL7603771A patent/NL7603771A/en not_active Application Discontinuation
- 1976-04-10 JP JP51039844A patent/JPS51127150A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| FR2307014B1 (en) | 1978-05-05 |
| IT1062067B (en) | 1983-06-25 |
| SE419095B (en) | 1981-07-13 |
| AU1283076A (en) | 1977-10-13 |
| JPS51127150A (en) | 1976-11-05 |
| SE7604081L (en) | 1976-10-11 |
| ZA761699B (en) | 1977-03-30 |
| FR2307014A1 (en) | 1976-11-05 |
| ES446861A1 (en) | 1977-06-01 |
| DE2615071A1 (en) | 1976-10-28 |
| NL7603771A (en) | 1976-10-12 |
| GB1543557A (en) | 1979-04-04 |
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