GB2168707A - Microcapsules for flameproofing polymeric material - Google Patents

Abstract

Microcapsules, each containing a mixture of a) a halogenated flameproofing organic compound (component a); and b) an inorganic oxide, hydroxide, borate or phosphate (component b), can be incorporated into polymeric material to flameproof the material. A preferred process for encapsulating comprises adding the substances to a cellulose acetate-phthalate solution l.p.o. urea and then adding a coacervating agent.

Description

SPECIFICATION Improvements in or relating to organic compounds The invention relates to a process for flameproofing polymeric material.

According to the invention there are provided microcapsules, each containing a mixture of (a) a halogenated flameproofing organic compound (component a); and (b) an inorganic oxide, hydroxide, borate or phosphate (component b).

Further, according to the invention there is provided a process for flameproofing a polymeric material comprising blending microcapsules containing a mixture of: (a) a halogenated flameproofing organic compound; and (b) an inorganic oxide, hydroxide, borate or phosphate with the polymeric material.

In this specification halogen is preferably chloro or bromo.

Preferably component (a) is a compound which is capable of flameproofing a polymeric substrate selected from those hereinafter defined.

Preferably component (a) is a chloro and/or bromo aliphatic, aromatic or heterocyclic compound, preferably containing 20 to 87% by weight Cl or Br, more preferably 40 to 80% by weight CI or Br. More preferably compound (a) is a compound selected from those that are solid at room temperature and have a melting point in the range 50 (preferably 75%) to 350"C. Most preferably component (a) is a compound in which the ratio of carbon atoms to halogen atoms is 5:1 to 1:1. Preferably component (a) has a particle size less than 50 Am, more preferably of less than 25 Am.

Especially preferred halogenated organic compounds are those selected from tetrabromophthalic acid anhydride; tetrabromo phthalic acid imide; bicyclo[2,2,1]heptan-2,3-dicarboxylic acid derivatives, such as the compound of the formula

terephthalic acid esters, such as bis-[2,3-dibromopropyl]-terephthalate; halogenated carbonates, such as 2,2-bis-bromomethyl-3-bromopropyl carbonate or tribromophenyl carbonate; halogenated diphenyls or diphenyleneoxides, such as decabromodiphenyleneoxide; octabromodiphenyleneoxide; brominated polymeric compounds, such as poly(tribromostyrene) and brominated polyphenylene ether; halogenated benzene, toluene, xylene or ethylbenzene, such as hexabromobenzene, pentabromotoluene, tetrabromoxylene, hexabromomethylbenzene and pentabromoethylbenzene; halogenated cycloaliphatic compounds, such as hexabromocyclodecane, methyhl-dibromocyclohexane, perchloropentacyclodecane or chlorinated paraffin with a chlorine content of 20 to 75% and halogenated bisphenols optionally diethoxylated, such as halogenated alkylaryl ethers, as for example 2,2-bis-(2',3'-dibromopropoxy)-3,5-dibromophenyl)propane and 1 ,2-bis(pentabromophe nyloxy)ethylene.

Of the especially preferred halogenated organic compounds the 20 to 75% chlorinated paraffins, the brominated cycloaliphatic compounds such as hexabromocyclododecane; and brominated diphenyls and diphenylenoxides such as octa- or decabromodiphenylene oxide and 1,2bis(pentabromophenylenoxy)ethylene are most preferred.

Preferred diphenyl and diphenylethers are those of the formula

where n is O or 1 x and y independently are integers from 2 to 5 inclusive.

Preferably component (b) is selected from oxides, hydroxides, borates and phosphates of Mg, B, Al, Si, Sn, Sb, Bi, Ti, Fe, Zn, Mo and W.

Component (b) is more preferably selected from the hydroxides of Mg and Al, the oxides of Sb and Bi and zinc borate, most preferably from Sb20s, Sb2O3 and zinc borate, especially Sub203.

The ratio of component (a) to component (b) is preferably 5:1 to 1:2, more preferably 4:1 to 1:1, most preferably 3:1 to 3:2 by weight.

Preferably the microcapsules have a diameter of up to 100 ,um, more preferably up to 75 m, most preferably up to 50 im and preferably have a wall thickness with a phase ratio of from 1:1 to 150:1, more preferably 5:1 to 100:1, most preferably 25:1 to 75:1.

"Phase ratio" is a term of the art being the weight ratio between the encapsulated material and the encapsulating material. The term "membrane" is also a term of the art referring to the encapsulating material when in the form of a capsule wall.

Preferred polymeric substrates which can be flameproofed according to the invention are selected from polyolefins (especially polyethylene and polypropylene and copolymers thereof); polyester such as polyethyleneterephthalate, polybutylene-terephthalate or unsaturated polyester resin; polyamide such as nylon; polyacrylate and polymethacrylate such as PMMA, polystyrene, ABS polymers, polyurethane, polyacrylonitrile and copolymers thereof, cellulose esters, epoxy resins and PVC.

The compositions according to the invention can be worked into the polymers by known methods. For example they can be added to the monomers or prepolymers or mixed with the finished polymer and worked in during extruding of the polymer. The compositions according to the invention can be used in the form of a master batch containing preferably 20 to 90%, more preferably 40 to 80% by weight of the microcapsules according to the invention and preferably 80 to 10%, more preferably 60 to 20% by weight of a solid polymeric material which is identical or compatible with the material to be flameproofed. The compositions according to the invention may also be used in the form of a suspension containing preferably 20 to 90%, more preferably 40 to 80% by weight of the microcapsules of the invention and the remainder being a liquid to form the suspension.

The encapsulating material of the microcapsules is usually polymeric or organic material insoluble in the polymer to be flame-proofed and is such that it maintains the microcapsules as discrete units when worked into the polymeric material but breaks at a temperature approaching (preferably 10 to 500 below the temperature at which the polymer burns) that of burning of the polymer to be flamproofed (i.e. about 200"C or more).

The encapsulating material is preferably gum arabic, gelatin, cellulose acetate phthalate or phenol-formaldehyde resins.

Components (a) and (b) can be encapsulated by known methods e.g. USP 4,460,563 or according to Examples 4 to 6.

It is an important feature of the invention to use capsules containing (a) and (b). If one does not encapsulate components (a) and (b) in the microcapsules it has been found that the following disadvantages may occur.

(1) When the flameproofed polymeric material is worked into the polymeric material, corrosion of the apparatus for working in the flameproofing material may occur; (2) In some polymeric substrates the halogenated organic compounds tend to migrate to the surface of the polymeric materials whereas in encapsulated form they do not; (3) Many halogenated organic compounds are volatile at the temperature required to work them into the polymer; and (4) The light stability is worsened particularly where there is interaction with light stabilisers already present.

A surprising feature of the invention is that by encapsulating components (a) and (b) in the same microcapsule, lower concentrations of each can be used, compared to homogeneous mixing in the substrate.

The encapsulating components (a) and (b) are incorporated into the polymer and remain in microcapsules in the polymer. However, if the temperature of any part of the polymer approaches burning (e.g. usually 200"C or more) the capsules break.

Preferably, further according to the invention, there is provided a process for microencapsulating one or more substances comprising adding the one or more substances to a cellulose acetate phthalate solution in the presence of urea and then adding a coacervating agent.

Preferably the coacervating agent is sodium sulphate.

Preferably the ratio of coacervating agent to the cellulose acetate phthalate is 20:1 to 5:1 by weight.

Preferably the ratio of urea to cellulose acetate phthalate is 1:2 to 2:1 by weight.

The invention will now be illustrated by the following Examples in which all parts and percentages are by weight and all temperatures are in "C unless indicated to the contrary.

Example 1 10 Parts of microcapsules containing a 70% chlorinated paraffin (CP 70-Hoechst) and Sb2O3 in a 2:1 ratio by weight are blended with 90 parts of a commercial high pressure polyethylene (Lupolen 2420 F-BASF) having a melt flow index (MFI) (190 /2.16 kp) 0.6 to 0.9 in a rolling mill. From the resulting rolled mass, plates of 3 mm thickness are produced at 1500 under a pressure of 1.25 kg/cm2 and subsequently 18.75 kg/cm2 for 1'/2 minutes each.The inflammability is tested according to U.L. (Underwriters Laboratories Inc.) 94 Test and the resulting classification is V-2 Example 2 20 Parts of the same microcapsules as used in Example 1 are blended with 80 parts of a commercial ABS (acrylonitrile/butadiene/styrene co-polymer-Cycloac T 10 000) in a rolling mill at 162 /152 over 3 minutes. Plates 3 mm thick are produced from the rolled mass at a pressure of 2 tonnes and 30 tones at 2100, respectively for 11/2 minutes each. The inflammability is tested according to U.L. 94 Test and the resulting classification is V-O.

If one blends the same mixture of chlorinated paraffin and Sub203 in non-encapsulated from with ABS the result is that there is no classification under the U.L. 94 Test.

The U.L. 94 Test is a flameproofing test for a flameproofed substrate. V-O is the optimal classification in this test. There are two other classifications V-l and V-2. If a substrate is given no classification it is held to be too inflammable to pass this test-that is to say for commercial purposes the substrate is not considered to be flameproofed under this test.

Example 3 20 Parts of microcapsules containing octabromodiphenyloxide and Sb203 in a 5:3 ratio are blended in a similar fashion to that of Example 2 with 80 parts of ABS and tested according to the UL. 94 Test and the resulting classification is V-O.

The encapsulating material of Examples 1 to 3 is cellulose acetate phthalate as described in Example 6.

Example 4 Microencapsulation of components (a) and (b) with a gelatin/gum arabic membrane can be achieved as follows: 50 g of 10% gelatin/water solution and 50 g of a 10% gum arabic/water solution are placed into a beaker and whilst stirring the resulting mixture is diluted with 400 ccs of water at 45".

66.7 g of the chlorinated paraffin of Example 1 and 33.3 g of Sub203 are put into the mixture.

Agitation is carried out until a homogeneous dispersion occurs.

A 10% acetic acid solution is added to bring the pH to about 4. At this pH the gelatin/gum arabic mixture will form a separate phase as a membrane around the particles of the chlorinated paraffin and Sub203.

The content of the beaker is slowly (over 20 minutes) cooled to approximately 25 and is then rapidly (within 2 minutes) cooled down to approximately 10 . This solidifies the gelatin/gum arabic membrane.

40 mls of 25% glutaraldehyde are added to harden the membrane and agitation is continued for 8 hours until total polymerisation has occurred. The microcapsules are then washed and dried.

Example 5 Microencapsulation of components (a) and (b) with a gelatin membrane can be achieved as follows: 100 g of a 10% gelatin/water solution are placed in a beaker at a temperature of approximately 45". Whilst being agitated the solution is diluted with 250 cc of water and 20 g of 5% hexametaphosphate/water. Whilst still being agitated, 66.7 g of the chlorinated paraffin of Example 1 and 33.3 g of Sb203 are added. After a homogeneous mixture has formed the pH is brought to approximately 4 by the addition of 10% acetic acid to cause the gelatin to form a separate phase as a membrane around the particles of the chlorinated paraffin and Sub203.

Solidification, hardening and drying is carrid out as in Example 4.

Hexametaphosphate is a product sold by Gross Guiglio SPA Example 6 Microencapsulation of components (a) and (b) using a cellulose acetate-phthalate membrane can be achieved as follows: A 5% aqueous solution of cellulose acetate-phthalate is made up. 40 g of this solution is placed in a beaker at ambient temperature and diluted with 150 ccs of water and 2 g of urea.

66.7 g of the chlorinated paraffin and 33.3 g of Sub203 were added and stirred until a homogeneous mixture is obtained. sodium sulphate is used to coacervate the cellulose acetate-phthalate around the particles of 70% chlorinated paraffin (sold under the tradename Electrofine) and Sb203.

After forming of the membrane has totally occurred, the pH is brought to 4 by the use of citric acid. Stirring continues until total coacervation has occurred. The microencapsules are then washed and dried.

Instead of using chloroparaffin, the same quantity of octa- or decabromodiphenyleneoxide or 1,2-bis(pentabromophenylenoxy) ethylene can be used.

Claims (15)

1. Microcapsules, containing a mixture of (a) a halogenated flameproofing organic compound (component a); and (b) an inorganic oxide, hydroxide, borate or phosphate (component b).

2. Microcapsules according to Claim 1, in which the halogenated flameproofing material is selected from tetrabromophthalic acid anhydride; tetrabromophthalic acid imide; bicyclo[2,2,1 ]heptan-2,3-dicarboxylic acid derivatives; terephthalic acid esters; halogenated carbonates; halogenated diphenyls and halogenated diphenyleneoxides; brominated polymeric compounds; halogenated benzene, toluene, xylene or ethylbenzene; halogenated cycloaliphatic compounds, halogenated bisphenol optionally diethoxylated.

3. Microcapsules according to Claim 1 or Claim 2, in which the halogenated flameproofing material is selected from 20 to 87% chlorinated paraffins, brominated cycloaliphatic compounds, and brominated diphenyls and diphenyleneoxides.

4. Microcapsules according to any one of the preceding claims, in which component (b) is selected from the oxides, hydroxides, borates and phosphates of Mg, B, Al, Si, Sn, Sb, Bi, Ti, Fe, Zn, Mo and W.

5. Microcapsules according to Claim 4, in which component (b) is selected from Sub205, Sub203 and zinc borate.

6. Microcapsules, substantially as herein described with reference to any one of Examples 1 to 6.

7. A process for flameproofing a polymeric material comprising blending microcapsules containing a mixture of: (a) a halogenated organic compound; and (b) an inorganic oxide, hydroxide, borate or phosphate with the polymeric material.

8. A process according to Claim 7, in which the halogenated flameproofing material is selected from tetrabromophthalic acid anhydride, tetrabromophthalic acid imide, bicyclo[2,2,1 ]heptan-2,3-dicarboxylic acid derivatives, terephthalic acid esters, halogenated carbonates, halogenated diphenyls and halogenated diphenyleneoxides, brominated polymeric compounds, halogenated benzene, toluene, xylene or ethylbenzene, halogenated cycloaliphatic compounds and halogenated bisphenols optionally diethoxylated.

9. A process according to Claim 8, in which component (a) is selected from 20-75% chlorinated paraffins, brominated cycloaliphatic compounds and brominated diphenyls and diphenyloxides.

10. A process according to any one of Claims 7 to 9, in which component (b) is selected from the oxides, hydroxides, borates and phosphates of Mg, B, Al, Si, Sn, Sb, Bi, Ti, Fe, Zn, Mo and W.

11. A process according to Claim 10, in which component (b) is selected from Sub205, Sb203 and zinc borate.

12. A process for flameproofing polymeric material substantially as herein described with reference to any one of Examples 1 to 6.

13. A polymeric substrate containing microcapsules according to any one of Claims 1 to 6.

14. A process for microencapsulating one or more substances comprising adding the substances to a cellulose acetate-phthalate solution in the presence of urea and then adding acoacervating agent.

15. A process according to Claim 14, substantially as herein described with reference to Example 6.