AU4199378A - Production of cross-linked polyolefine articles - Google Patents

Description

CONVENTION AUJSTRALIA

APPLICAT.CoN F~OR A PATENT

41 993/l8 I/Wet)W dTISH STEET, C0RPORATICN._0MZI

Aflamefa) of

OfW 33 Gr'osvenor Place, Applicantfs) London, S.W.1., England

,hereby -apply for the grant of a Patent for an invention entitled 1iiert frtaF THE PRODUCTION OF CROSS-LINKED POLYOLEFINE ARTICLES

which is described in the accompanying complete specification. 000

(Note: The following paragraph applies only to Convention applications)

cplcio ap*( This application is a Convention applicatOn based on the basic application(s) for a patent or similar protection identified ~yaui'ke., country, and filing date as follows:

S2927/77

GREAT BRITAIN

December, 1977

S 0a*500 S

0

0

S Address for Service: PHILLIPS ORMONDE AND FITZPATRICK S 50 S Patent and Trade Mark Attorneys S0 367 Collins Street 0* S S 0 Melbourne, Australia 3000 50

Insert DATE .Dated (g) of signing 27 November, 1978

(bi) signature t of ()PHILLIPS ORMONDE AND FITZPATRICK arlican (s) copoat'- Attorneys for: seebednot'o) BRITISH STEEL CORPORATION Corprate seal if a= Notei No legalization or other witness required

PIHILLIPS ORMONDE AND FITZPATRICK Patent and Trade Mark Attorneys SP 367 Collins Street Melbourne, Australia P17/11/77

VI 1) AU-A 41993/T8

(12) PATENT SPECIFICATION ABSTRACT (19) AU

(21) 41 993/T8 (22) 28.11.78 (23) 28.11.78 (24) 20.12.77 (31) 52927/77 (32) 20 12.77 (33) GB (43) 28.6.79 (51) C085 3/24 C08J 5/00 C08J 3/22 C08K 5/14 C08K 5/34 C08K 5/36 C08K 5/54 C08L 23/04 (54) PRODUCTION OF CROSS-LINKED P0LY0IEFINF, ARTICLES (71) 13RXTISR STEEL CORP. (72) DENNING J.A. AOD SUMMERS M.J. (74) P0 (57) 0LATM 1. Amethod of producing cross-li1nk' d polyo-efine articles

cor~prising the steps Of mixing thoroughly the polyolefine in

particulate form with a silane, an organic peroxide catalyst, and

stabilisinc, constituent, subsequently forming the mnixture into the

configurati.on of the article to be produced, and then carrying out

the step of cross linking of the material of che article.

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ALJTMAUA

Pdenu Act

CO.'MPLETE SPECIFICATION (ORIGINAL)

4 993 /78 Ca It. Class Apnlication Number: Lodged:

Conmplet-, Specification Lodged;

Accepted; Published: /jA~

0

0 ;Related Art:

S 0655 0 OeOS

APPUCANTSREF.: Case No. P.8025/Australia Name(s) of AppIlcan.~(s): BRITISH STEEL CORPORATION @0 ~b S S A SO 0U S. ~~ddress((,J) or Applicant(s): 33 Grosvenor Place, 0

S London S.W.1, C England S *00000 ~Ctuii~ InvCnt~~(s): john Allan Denning 9 @6 Michael John Summers S S.

5* 0 S. 0*

Address for Service is: PHILLIPS, ORMONDE FITZPATRICK Patent and Tiade Mark At'orneys 367 Collins Stre/t Melbourne, Australia, 3000 Complete Specification for the invention entitied:

THE PRODUCTION OF CROSS-LINKED POLYOLEFINE ARTICLES

The following statement is a full description of this invention, including the best method of performing it known to applicant(s):

P 19/11/77

This invention relates to the production of cross-

linked polyolefine articles.

It is known to modify the properties of polyethyiene

and other olefinic polymer articles by cross linking the

polymers. This can be done with the aid of an organic

peroxide catalyst and reaction with a silane. An example

of such a cross-linking operation is set out in United

Kingdom Patent Specification No. 1,286,460. _41 4 The effect of such cross linking can be most benefi- S

cial. Thus pipes formed of cross-linked polyethylene have 1 0S S S greatly increased resistance to deformation with tempera- *5

S ture changes and are therefore able, for example, to carry S

@055 hot fluids such as hot water.

It is an object of the present invention to provide

a convenient practical arrangement for the production of

cross-linkable olefinic polymer articles.

According to the invention there is provided a method S of producing cross-linked polyolefine articles comprising

the steps of mixing thoroughly the polyolefine in particu-

20 late form with a silane, an organic peroxide catalyst, and S S 0 stabilising constituent, subsequently forming the mixture

into the configuration of the article to be produced; and

then carrying out the step of cross linking of the material

of the article.

We have found that it is possible to prepare the mir-

ture ready for forming into the article concerned as defined above in what is essentially a single-stage operation. The mixture so produced can, if desired, be stored in air-tight containers or bags for several days and still be usable directly to form the article concerned.

The polyolefine may be a high or medium density

C polyethylene or a copolymer with such polyethylene, and the mixture may be used, as produced, in the ,-4 me me extrusion of pipe, for example. Again, we have found e 10 the invention particularly useful in the production S by injection moulding of pipe fittings.

Whilst the particulate form of the polyolefine 0*

S. may comprise pellets or granules, we have found that S

the invention is particuldrly effective wher- the

polyolefine is more finely divided so that the

polyolefine may advantageously be a powder. The 0O

silane may be one of the type described in detail in 0:a 0 0

U.K. Patent No. 1,286,460, and in particular may e 0 corrprise vinyl trimethoxysilane.

The organic peroxide may be one of many known in 00 6 the art such as dicumyl peroxide, tertiary butyl per-

pivalate, or 1-3 bis (tertiary butylperoxyisopropyl) benzene.

The stabilising constituent may comprise a single

antioxidant of known type, or a mixture of two or more

ancioxidants, or one or more such antioxidants with one or more ultra-v{olet light degredation stabilisers of known type.

A suitable colour pigment may be added to the mexture during

its production.

We have found the cross linking of the material of articles

produced in accordance with the invention can be obtained without the

use of further catalysts of the known silanol condensation kind, and

<y that satisfactory cross linking can be achieved by subjecting the

articles to low pressure steam or hot water.

One example of the production of polyethylene water pipe and S

1t fittings will now be given. 0 go

The required quantity of high density polyethylene powder is S

weighed into a high speed mixer of known type. 555554

An appropriate pigment (to the quantity of up to may be

added to the polymer either by itself or premixed with a small amount

of polymer to aid dispersion. It is to be noted that alternatively

Sthe pigment can be added mixed in with the silane or in the silane

Swith organic peroxide. In one particular instance the pigment

Scomprises 0.500% Irgalite Yellow WSR plus 0.001 Cromophtal Green GFN S

Splus 0.006% Carbon Black, plus 0.020 Titanium dioxide. The polymer S.

and pigment is mixed until complete dispersion has ucen achieved. 0O*

The required stabilisers can also be mixed into the polymer at the

same time as the pigment, or as a separate mixing operation, or in

the form of a slurry mixed into the whole of, or part of, the

vinyltrimethoxysilane/peroxide solution.

A 1.5% to 5% (typically by volume quantity (relative to

the polymer) of silane vinyl trimethoxysilane) is now taken.

lr

To this is added 0.01% to 5% (typically 0.10%) by weight of the

polymer of an organic peroxide catalyst sold under the trade name

of "Perkadox 14" (1-3 bis (tertiary butyperoxyisopropl) benzene,

and mixed until dissolved or as much as possible is in solution.

Depending on the method chosen, this solution can then be

added to the polymer mix, or the required amounts of stabilisers C c added to the whole of, or part of, this solution, and the slurry 011 so formed along with the remainder, if any of the vinyl/trimethoxy-

silane/peroxide solution, added to the contents of the mixes.

I 'iThe stabilisers used will be up to 4% by weight of polymer and

will typic Lly comprise 0.4% of "Irganox 1035" Thiodiethanol- b is L3(3.5-di-t-butyl-4-hydroxyphenyl) propionate] and 0.25% of

"Tinuvin 326" (2-2'-hydroxy-3'-tert butyl-5'-methylpentyl)-3-

chlorobenzotriazole).

The total constituents of the mixer are mixed for two minutes,

S or for as long as is needed to provide complete dispersion of all

added materials through the polymer. If a lengthy mix is needed, 0

loss of silane due to frictional heat may occur, in which case a

S cooled mixer may be used. In some instances means for returning

.2t silane vapour to the mixer may be required.

After mixing, the material may be bagged or stored in air-

tight containers until required for a pipe extrusion machine. If

stored in air-tight containers the material can be kept for several

days, although storage in bags can obviously be only for a

considerably lesser time due to problems of evaportion. We have

found in any event that a storage period is beneficial in that it encourage$ absorption of the silane by the polymer.

The material is fed as required by any suitable means into a

pipe extruder maintained in the temperature range of 180 0 C to 240°C

dependent on the peroxide and polymer used (typically slightly in

excess of 215°C).

Cross linking of the extruded pipes was achieved by steam

autoc8ving at 12 0°C. '-4 @05 Injection -moulded fittings are produced from the material

using the same production temperature ranges, and the same 0 autoclaving conditions. Sg 0*

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Claims (11)

The claims defining the invention are as follows:-

1. A method of producing cross-linked polyolefine articles

comprising the steps of mixing thoroughly the polyolefine in

particulate form with a silane, an organic peroxide catalyst, and

Sstabilising constituent, subsequently forming the mixture into the

eg configuration of the article to be produced, and then carrying out Cr C« the step of cross linking of the material of the article.

2. A method as claimed in claim 1 wherein the polyolefine is a

high or medium density polyethylene.

3. A method as claimed in claim 1 wherein the polyolefine is a 0* copolymer including polyethylene.

4. A method as claimed in anyone of the preceding claims in which

the polyolefine is in the form of a powder.

5. A method as claimed in any one of the preceding claims e wherein said mixture is extruded in the form of a pipe.

6. A method as claimed in any one of claims 1 to 4 wherein sa.d

mixture is injection moulded as pipe fittings. s

7. A method as claimed in any one of the preceding claims

wherein a colour pigment is added to the mixture during its

production.

8. A method as claimed in any one of the preceding claims

wherein the silane comprises vinyl trimethoxysilane.

9. A method as claimed in any one of the preceding claims

wherein the stabilising constituent comprises a mixture of one

or more antioxidants with one or more ultra-violet light

degradation stabilisers.

10. A method of producing cross-linked polyolefine articles

substantially as hereinbefore described in relation to the example.

11. Cross-linked polyolefine articles produced in accordance

with the method claimed in any one of the preceding claims. C 0 0

0 0

t0 1

DATED 27 November, 1978

PHILLIPS ORMONDE AND FITZPATPICK Attorneys for: BRITISH STEEL CORPORATION

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