GB2509128A

GB2509128A - Process for improving fire resistance of an organic polymer

Info

Publication number: GB2509128A
Application number: GB1223170.0A
Authority: GB
Inventors: Christophe Paulo; Mert Kilinc; David Pierre
Original assignee: Dow Corning Corp
Current assignee: Dow Silicones Corp
Priority date: 2012-12-20
Filing date: 2012-12-20
Publication date: 2014-06-25
Also published as: GB201223170D0

Abstract

A process for improving fire resistance of an organic polymer having unsaturated groups comprising addition to the organic polymer silane or siloxane compound being free of phosphorous and containing at least one of the following function: vinyl unsaturation, acrylate, primary, secondary amine, SiH which function will react with the unsaturation of the organic polymer in the presence of radical initiator means. Also disclosed is a fire resistant polymer composition comprising an organic polymer having unsaturated groups and a silane or siloxane compound free of phosphorous and containing at least one of the following function: vinyl unsaturation, acrylate, primary, secondary amine, SiH; and use of the fire resistant composition.

Description

PROCESS FOR IMPROVING THE FIRE RESISTANCE OF AN ORGANIC POLYMER

[0001] The invention is directed towards a process for improving the fire resistance of an organic polymer, a fire resistant polymer composition and the use of a silane or siloxane to improve the fire resistance of a composition.

[0002] It is known that the fire resistance of organic polymers can be enhanced by the addition of compounds able to reduce the flammability or provide other desirable properties in case of fire for example anti-dripping properties. An organic polymer is a polymer which contains carbon/carbon bonds. in the polymer backbone [0003] For example, the paper Thermal degradation behaviours and flame retardancy of PC/ABS with novel silicon-containing flame retardant' by Hanfang Zhong et al. in Fire.

Mater. Vol. 31, 411-423 (2007) describes a novel flame retardant containing silicon, phosphorus and nitrogen synthesised from the reaction of 9,1 0-dihydro-oxa-1 0- phosphaphenanthrene-lO-oxide (DOPO), vinylmethyldimethoxysilane and N-p- (aminoethyl)--aminopropyl methyl dimethoxy silane.

[0004] W0201 1/143930 describes a process foF improving the fire resistance of a thermoplastic or thermoset organic polymer composition, characterised in that an alkoxysilane containing at east one organic nitrogen-containing group and an alkoxysilane or silicone resin containing at least one group selected from phosphonate and phosphinate groups are added to a thermoplastic or thermosetting organic polymer composition and heated in the presence of moisture to cause hydrolysis and siloxane condensation of the alkoxysilane or alkoxysilanes. The alkoxysilanes, or alkoxysilane(s) and silicone resin, of the invention are particularly effective in increasing the lire resistance of polycarbonates and blends of polycarbonate with other resins such as polycarbonate/ABS blends.

[0005] It is desirable to provide a process for improving the fire resistance of an organic polymer containing unsaturated groups by adding to the organic polymer a compound which is free of phosphorous. Phosphorous-containing compounds are sometimes expensive and may have a detrimental effect on the electrical properties of the formed material.

[0006] Therefore, in one of its aspects, the invention provides a process for improving the *r": 30 fire resistance of an organic polymer containing unsaturated groups wherein a silane or ". : siloxane compound is added to the organic polymer said silane or siloxane compound being free of phosphorous and containing at least one of the following function: vinyl unsaturation, acrylate, primary amine, secondary amine, SiH which function will react with * the unsaturations of the organic polymer in the presence of means able to initiate radical * 35 reactions.

[0007] The silane or siloxane compound added to the organic polymer (henceforth referred to as the additional compound) may be a silane containing Si-C bond(s) or a siloxane containing Si-O bond(s). When it is a siloxane it can be a simple siloxane containing only one Si atom or a polysiloxane containing several Si-O-Si bonds especially an organopolysiloxane (silicone). It can be a silicone resin containing T (RSiO,,) and/or Q units (5104,2) where R is especially an aliphatic or aromatic moiety.

[0008] Said organic polymer containing unsaturated groups may be thermoset or thermoplastia It is preferably thermoplastic as thermoset polymers can be degraded in case of heating.

(0009] The organic polymer must contain unsaturated groups able to react with the functional silane or siloxane. Preferably, the organic polymer contains C=C and/or CN unsaturations. Preferably the carbon/carbon unsaturations are not contained in an aromatic moiety such as for example an aromatic ring as those kind of unsaturated groups will not be able to react with silane or siloxane.

(0010] The organic polymer is preferably selected from ABS. SBS and diene elastomer.

ABS (acrylonitrile styrene butadiene) is a thermoplastic terpolymer made by polymerizing styrene and acrylonitrile in the presence of polybutadiene.

(0011] These polymers are elastomeric and improve the mechanical properties of materials made thereof. Similar product is Styrene-Butadiene-Styrene (SBS) -same structure without acrylonitrile.

(0012] As conversion of the polymerization is not 100%, a high amount of double bonds in the polybutadiene of ABS and SBS remain unsaturated.

(0013] In another preferred embodiment, the organic polymer is a diene elastomer. By a diene elastomer we mean a polymer having elastic properties at room temperature, mixing temperature or at the usage temperature, which can be polymerized from a diene monomer Typically, a diene elastomer is a polymer containing at least one ene (carbon-carbon double bond, C=C) having a hydrogen atom on the alpha carbon next to the C=C bond. The diene elastomer can be a natural polymer such as natural rubber or can be a synthetic polymer derived at least in part from a diene.

The organic polymer containing unsaturations can be part of a polymer matrix containing at * least 2 different polymers, for example an ABS/polycarbonate matrix.

(0014] There are several possible ways to initiate radical reactions. The means for initiating radical reactions can be the addition of a radical initiator compound such as, preferably, a peroxide. It can be the application of heat, for example in case of a fire. It can further be formed by ultraviolet radiations or electron beam irradiation.

(0015] The silane or siloxane compound may contain a primary or secondary amino * 35 function. Such amino functions can for example react with unsaturated C=C or or CeC *** functions following Michael's addition.

[0016] The compound containing at least one primary amine group can for example be 3- aminopropyltrimethoxysilane, 3-amino-2-methyl-propyltrimethoxysilane or 3- aminopropyltriethoxysilane, or can be a disiloxane such as bis(3-aminopropyl)-tetramethoxysilane. A compound containing at least one secondary amine group can for S example be N-methyl-3-aminopropyltrimethoxysilane or N-phenyl-3-aminopropyltrimethoxysilane. A compound containing a primary amine group and a secondary amine group can fpr example be N-(2-aminoethyl)-3-aminopropyltrimethoxysilane. The aminoalkylalkoxysilane can alternatively be a dialkoxysilane or monoalkoxysilane. A compound containing at least one primary amine group can for example be 3-aminopropylmethyldimethoxysilane or 3-aminopropylmethyldimethoxysilane [0017] In one preferred embodiment, the compound is a siloxane, more precisely an amino functional silicone resin. Several aminosiloxanes are available for example it can be an aminosiloxane according to US7501473 the content of which being incorporated herein by reference. US7501473 describes an amino functional silicone resin containing aryl functionalities, RR'SiO2 and amine content.

[0018] In other preferred embodiments, the compound is an aminoalkylsilane.

(0019] In other preferred embodiment, the compound is a siloxane or a silane containing an acrylate function, for example an acrylate alkyl silane.

100201 It can include an acrylate-functional alkoxysilane such as acryloxyalkylsilanes for example y-acryloxypropyltrimethoxysilane, acryloxymethyltrimethoxysilane, acryloxymethylmethyldimethoxysilane, acryloxymethyldimethylmethoxysilane, y-acryloxypropylmethyldimethoxysilane or y-acryloxypropyldimethylmethoxysilane.

(0021J In some preferred embodiments, the siloxane compound is a vinyl siloxane or a vinyl silicone resin. Unsaturated functions of the organic polymer may react with unsaturated C=C linkages following a poly-addition reaction, especially in the presence of free radicals generators. For example the added compound can be a linear organopolysiloxane chain comprising pendant vinyl groups, for example hexenyl groups. It can be a silicone resin containing T and/or Q units and some terminal or pendant vinyl * 30 unsaturations.

10022] In some preferred embodiments, the siloxane compound is a siloxane containing SIH function(s). For example the SiH siloxane is dimethylmethyl hydrogen siloxane. SiH functions can react with other unsaturated linkages by the hydrosilylation reaction, in the presence of free radical generators and/or Pt catalysts.

[0023] In still other preferred embodiments, the compound is a mixture of at least 2 different silane or siloxane compounds.

[0024] The invention also provides a fire resistant polymer composition containing a mixture or a reaction product obtained from (1) an organic polymer containing unsaturations and (2) a silane or siloxane compound being free of phosphorous and which contains at least S one of the following function: vinyl unsaturation, acrylate, primary amine, secondary amine, Sift [0025] The fire resistant composition according to the invention can be a physical mixture of an organic polymer containing unsaturations and a silane or siloxane compound. In other preferred embodiments, the composition is a reaction product of an organic polymer containing unsaturations with a silane or siloxane compound.

[0026] Preferably, the silane or siloxane compound (2) is present in an amount ranging from 0.1 to 40% by weight of the composition containing (1) and (2).

[0027] Preferably, the fire resistant polymer composition according to the invention is halogen free. Halogen containing flame retardants have performed well in terms of flame is retardancy properties, processability, cost, etc, however there is an urgent need for halogen-free flame retardants (HFFR) as polymer additives, which comply with environmental regulations, OEM perception, customers requirements, etc. Fire safety is now based on preventing ignition and reducing flame spread through reducing the rate of heat release, as well as on reducing fire toxicity. Flame retardant additives must be safe in what concerns health and environment, must be cost efficient and maintain/improve plastics or rubbers performance.

[0028] The halogenated flame retardant compounds act mostly in the gas phase by a radical mechanism to interrupt the exothermic processes and to suppress combustion.

Examples are the bromine compounds, such as tetrabromobisphenol A, chlorine compounds, halogenated phosphate ester, etc. [0029] In some preferred embodiments, the composition further contains a flame retardant additive. Among the halogen-free flame retardants one can find the metal hydroxides, such as magnesium hydroxide (Mg(OH)2) or aluminium hydroxide (Al(OH)3), which act by heat :. absorbance, i.e. endothermic decomposition into the respective oxides and water when : 30 heated, however they present low flame retardancy efficiency, low thermal stability and significant deterioration of the physical/chemical properties of the polymer matrices. Other ° compounds act mostly on the condensed phase, such as expandable graphite, zinc borate, and nanoclays are other examples of halogen-free flame retardants. Silicon-containing * additives are known to significantly improve the flame retardancy, acting both through char * 35 formation in the condensed phase and by the trapping of active radicals in the vapour * phase. Sulfur-containing salts, such as potassium diphenylsulfone sulfonate (KSS), are effective flame retardant additives for thermoplastics.

[0030] The invention further provides a fire resistant composition wherein the composition further contains pigment and/or filler. The fire resistant composition of the invention can contain additives such as fillers, pigments, dyes, plasticisers, adhesion promoters, coupling agents, antioxidants, impact resistants, hardeners (e.g. for anti-scratch) and/or light S stabilisers.

10031] The composition can further contain an anti-dripping agent such as for example polytetrafluoroethylene to prevent dripping of the material in case of fire.

(0032] In particular the polymer compositions of the invention can contain a reinforcing filler such as silica. The silica is preferably blended with the compound (2), before the compound (2) is added to the organic polymer containing unsaturations. The silica can for example be present at 0.1 or 0.5% by weight up to 40 or 60% by weight of the polymer composition, and can be present at ito 500% based on the total weight of compound (2).

[0033] The invention further extends to the use of a silane or siloxane compound being free of phosphorous and which contains at least one of the following function: vinyl unsaturation, acrylate, primary amine, secondary amine, SiH to improve the fire resistance of an organic polymer containing unsaturations.

[0034] The invention is illustrated by the following examples, in which parts and percentages are by weight.

Prophetic examples

Prophetic example I

[0035] 10% of amino siloxane resin DC3055 will be added to ABS granules and mixed through extrusion process (temperature between 220-290°C). The extrudate will then be cooled down and (re)-pelletized to form modified ABS granules. These granules will then moulded into their end-use shape.

[0036] The granules will be also extruded and injected into UL94-bars for fire resistance evaluation. In the UL-94 test, a flame is applied to a vertically disposed sample of a 120mm x 12mm x 1.6mm. The sample self-extinguishing time will be evaluated by observing the flaming time. One will also observe if the sample exhibits dripping or not. One will also : examine the behaviour of the material according to the cone calorimeter test where a * r 30 radiant heater of conical shape produces a heat flux over the sample under study. The . : smoke density under fire conditions can also be observed.

[0037] During the fire test, the amino groups of amino siloxane resin can further react with the unsaturated bonds of ABS to re-build a network while the product is degraded and hence reduce dripping and fire evolution. The amino groups already reacted during sample * 35 preparation will give additional heat resistance to ABS because they already created a * resistant network based on Si-O-Si bond with ABS polymeric chains.

Prophetic example 2

[00381 20% of acryloxymethyltrimethoxysilane and 3 phr Luperox ® 230 organic peroxide parts will be added to 100 pts ABS granules and will be mixed through extrusion process (between 220-290°C). The extrudate will then be cooled dawn and (re)-pelletized to form modified ABS granules. These granules will then be moulded into their end-use shape.

The granules will also be extruded and injected into UL94-bàrs for fire resistance evaluation.

Prophetic Example 3

[0039] 10% by weight of linear vinyl siloxane DC7690 and 2 phr Luperox @801 organic peroxide will be added to ABS granules and will be mixed through extrusion process (between 220-290°C). The extrudate will then be cooled down and (re)-pelletized to form modified ABS granules. These granules will then be moulded into their end-use shape.

[0040] The granules will also be extruded and will be injected into UL94-bars for fire resistance evaluation.

[0041] During the fire test, the unsaturated bonds can further react with the unsaturated bonds of ABS to re-build a network while the product is degraded and hence reduce dripping and fire evolution. The unsaturated groups already reacted during sample preparation give additional heat resistance to ABS because they already created a resistant network based on Si-O-Si bond with ABS polymeric chains.

Prophetic Example 4

[0042] 25% of dimethyl methyl hydrogen silane DC2-7672 and 3 pbr Luperox @230 organic peroxide will be added to ABS granules and will be mixed through extrusion process (between 220-290°C). The extrudate will be then cooled down and (re)-pelletized to form modified ABS granules. These granules will be moulded into their end-use shape.

[00431 The granules will also be extruded and injected into UL94-bars for fire resistance evaluation.

[00441 During the fire test, the unsaturated bonds can further react with the unsaturated bonds of ABS to re-build a network while the product is degraded and hence reduce dripping and fire evolution. The unsaturated groups already reacted during sample * * preparation give additional heat resistance to ABS because they already created a * r * 30 resistant network based on Si-O-Si bond with ABS polymeric chains. ** * * * * * S.

S 0

S

Claims

CLAIMS1. A process for improving the fire resistance clan organic polymer containing unsaturated groups wherein a silane or siloxane compound is added to the organic polymer said silane or siloxane compound being free of phosphorous and containing at least one of the following function: vinyl unsaturation, acrylate, primary amine, secondary amine, SiH which function wilt react with the unsaturations of the organic polymer in the presence of means able to initiate radical reactions.
2. The process according to claim 1 wherein the organic polymer is thermoplastic.
3. The process according to claim 1 or 2 wherein the organic polymer contains CC and/or CN unsaturations.
4. The process according to claim 2 wherein the organic polymer is selected from ABS, SBS and diene elastomer.
5. The process according to any preceding claim, wherein the means able to initiate radical reactions are addition of radical initiator compound preferably a peroxide or application of heat or ultraviolet radiations or electron beam irradiation.
6. The process according to any preceding claim, wherein the siloxane compound is an amino functional silicone resin.
7. The process according to any preceding claim, wherein the silane compound is an aminoalkylsilane.
8. The process according to any preceding claim, wherein the silane compound is an acrylate alkyl silane.
9. The process according to any preceding claim, wherein the siloxane compound is a vinyl siloxane or a vinyl silicone resin.
10. The process according to any preceding claim, wherein the siloxane compound is a SiH siloxane.
11. 11. A fire resistant polymer composition containing a mixture or a reaction product obtained from (1) an organic polymer containing unsaturated groups and (2) a silane or siloxane compound. being free of phosphorous and which contains at least one of the following function: vinyl unsaturation, acrylate, primary amine, secondary amine, * . SiH.
12. Afire resistant polymer composition according to claim 11 wherein the silane or siloxane compound (2) is present in an amount ranging from 0.1 to 40% by weight ofthe composition. Is this in description?
13. A fire resistant polymer composition according to claim 11 or 12 which is halogen free.
14. A fire resistant composition according to any of claims 11 to 13 wherein the composition further contains a flame retardant additive.S
15. A fire resistant composition according to any of claims 11 to 14 wherein the composition further contains additives such as fillers, pigments, dyes, plasticisers, adhesion promoters, coupling agents, antioxidants, impact resistants, hardeners and/or light stabilisers.
16. The fire resistant composition according to any of claims 11 to 14 wherein the composition further contains an anti-dripping agent preferably polytetrafluoroethylene.
17. Use of a silane or siloxane compound being free of phosphorous and which contains at least one of the following function: vinyl unsaturation, acrylate, primary amine, secondary amine, SiH to improve the fire resistance of an organic polymer containing unsaturatio ns. *. .* * * . * . * * * . * S * **5*S** * *