NZ202379A - Strippable coating compositions containing atactic polypropylene - Google Patents

Description

New Zealand Paient Spedficaiion for Paient Number £02379 20Z31Q Date: 17 December 19-82 (Post-dated from 4 November 1982) COMPLETE SPECIFICATION STRIPPABLE COATING SYSTEM #We, AH I OPERATIONS LIMITED, a New Zealand company of 640 Great South Road, Manukau, Auckland, New Zealand hereby declare the invention for which TP/ we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- 202373 This invention relates to a strippable coding composition and a method for temporarily protecting surfaces by applying the coating thereto.

Non-porous surfaces such as anodised aluminium or other metal surfaces may require temporary protection from surface scratching or corrosion during transport or while the materials are being worked such as when a building is being erected. Motor vehicles during delivery, particularly during sea transport, require a temporary form of surface protection which can be readily removed.

Vinyl and nitrocellulose strippable coatings are used for such purposes. Such coatings have many disadvantages such as residual staining and high price It is an object of this invention to go sore way towards obviating these disadvantages or at least to provide the public with a useful choice.

Accordingly the invention may be said broadly to consist in a dry mix composition capable of forming a thixotropic solution in anorganic "solvent, the composition comprising: Component Polymer of Formula I Anti-oxidant Modi fier Filler % By Weight of Cosoosition -80 Up to 5 Up to 70 Up to 80 202379 wherein said polymer of Formula I is an atactic polypropylene of the formula:- CH CH.

CH CH. n wherein n is equal to 50 to 200 in one embodiment having a lower molecular weight, and n is equal to 200 to 1000 in another embodiment having a higher molecular weight.

Atactic polypropylene is a by-product of a process for polymerizing polypropylene. The amount and type produced can be varied widely depending on the polymerization reaction conditions and methods of separation. Lower molecular weight grades have a molecular weight of 3,000 to 12,000 while higher molecular weight grades have a molecular weight of 12,000 to 56,000.

Preferably the anti-oxidant is a heat stabiliser such as di-tertiary butyl p-cresol or other known oxidation inhibitor.

Preferably said modifier is a resin, rubber elastomer or wax.

Preferably said resin is an aliphatic hydrocarbon such as ethylene vinyl acetate of low vinyl acetate content, ethylene vinyl ester of low vinyl ester content, polyethylene, polyphenylene or polybutene.

Preferably said rubber elastomer, is selected from the group con sisting of ethylene/propylene, (ethylene/propylene diene monomer) ter-polymer, natural rubber, chlorobutadiene rubber, butyl rubber, and styrene block copolymers.

Preferably said wax is selected from the group consisting of a polyethylene wax, paraffin and a microcrystalline wax- Alternatively said modifier is tall oil rosin, polyterpene or wood rosin, pentaerythrite ester, methylstyrene vinyl toluene copolymer or hydrated colophonium.

Preferably said filler is selected from the group consisting of barium sulphate, chalk, lime, quartz, asbestos or synthetic fibres, talc and mixtures thereof.

Preferably said composition includes colour pigments such as a dye comprising inorganic pigments.

Preferably there is present 30 to 50% by weight of said polymer of Formula I.

In another embodiment the invention may be said broadly to consist in a solution of the composition defined above in an orqanic solvent.

Preferably said solvent is a mixture of organic solvents of relative evaporation five times faster than toluene.

Preferably said solvent comprises aromatic, aliphatic, cycloaliphatic or chlorinated hydrocarbons.

Preferably said solution has a concentration of 5 to 30% by weight of the solution.

Alternatively said solution has a concentration of 5% by weight. 202379 - Alternatively said solution has a concentration of 30% by weight. Preferably said solution is thixotropfc.

In a particularly preferred embodiment said solution has the following composition: In another embodiment the invention may be said broadly to consist in a solution of composition substantially as described in example I or example II.

In another alternative the invention may be said broadly to consist in a method of protecting non-porous surfaces which comprises applying thereto a solution as defined immediately above and allowing the solvent to evaporate to thereby form a protective coating.

Preferably said solution has a concentration of 5% by weight.

Alternatively a solution having a concentration of 30% by weight is used.

Preferably said solution is allowed to dry for 5 to 10 minutes at 20°C.

Component % by Weight of Solution Polymer of Formula I Gum Rosin Modifier Calcium Carbonate Di-tertiary Butyl p-cresol 2:1 Hexane/Toluene Blend -50 0 - 5 0-15 0.1 Balance £02379 Preferably said solution is applied to said surface at a coverage rate of 15 to 25 per litre.

Preferably said method includes the additional step of wiping said coating from a so-coated substrate using said solvent when protection is no longer required.

The invention consists in the foregoing and also envisages constructions of which the following gives examples.

EXAMPLE I A polymer of formula I, a modifier and an anti-oxidant, when used, were blended under stirring. Where a polymer of a lower molecular weight was employed it was dissolved by soaking in the solvent at room temperature. Alternatively it could be heated up to 90°C in the solvent. In the case of a higher molecular weight polyolefinic polymer the polymer was heated with the solvent. In such a case an anti-oxidant was used in order to inhibit degradation at prolonged elevated temperatures. Fillers were added, when required, prior to dilution. The concentrated solution was diluted as a final step. For both solutions A and B the solids concentration was. 5% and the modifiers, fillers and anti-oxidants used are set out below in table 1. 2.02379 TABLE I Component % by weight of composition A B Polymer of Formula I Gum Rosin Calcium Carbonate Di-tertiary Butyl p-cresol 2:1 Hexane/Toluene Blend 3.6 0.3 1.0 0.1 95 95 EXAMPLE II The procedure described in relation to example I was followed with the exception that in a final dilution step diluted the concentration of both solutions A and B was raised to 30%. The concentration of modifiers, fillers and anti-oxidants used is set out below in table II.

TABLE II Component % by wei ght A of compostion B Polymer of Formula I 21.4 Gum Rosin - 2.1 Calcium Carbonate - 6.4 Di-tertiary Butyl p-cresol - 0.1 2:1 Hexane/Toluene Blend 70 70 202379 EXAMPLE Ilf A 5% solution prepared according to Example I was applied to ano-dised aluminium by spraying equipment. It was found that after 10 minutes the solution had dried to a film of a thickness of approximately 50 ym without tackiness. The film could be readily removed by wiping with some of the solvent used to make the.coating solution.

EXAMPLE IV A 30% solution prepared according to Example II and applied by spraying equipment provided a continuous dry film of 150 ym. It was found to dry after 10 minutes at 20°C. The film could be removed by wiping with the solvent used to make the coating solution. Thicker films of 300ym and higher may also be removed by peeling.

EXAMPLE V A solution prepared as in Examples I and II and applied as in Examples III and IV produced a film which was found to have excellent resistance to aqueous solutions including strong acids and bases. Strongly oxidising agents such as fuming acids were found to attack the film and cause a loss in physical properties.

Anodized aluminium coated according to both examples III and IV was left for 12 hours in acid and basic solutions as listed in table III below. Standard Aluminium Associated Motar test was also carried out at 38°C 100% Relative Humidity for one week. After this the coatings were water rinsed and stripped off by wiping with a solvent 202379 and microscopic comparisons were .made against an uncoated anodized aluminium which had not been subjected to the same chemical attack. The quality of the finish of the anodized aluminium from which the coating had been stripped is given table III below.

TABLE III Concentration of Acid or Base % % % Concentrated ACIDS Sulphuric Ex Ex , Good Hydrochloric Ex Ex - Good Phosphoric Ex Ex Ex Good Nitri c Ex Ex - Poor Aceti c Ex Ex - - BASES Cement Paste - - - Excellent Potassium Hydroxide Ex Ex Ex - Sodium Silicate Ex Ex Ex - .

GENERAL DESCRIPTION The film produced by the methods of Examples III and IV was creamy white. It was found to give protection to anodised aluminium and other metal parts from moisture, corrosion, concrete splashes and foreign matter likely to scratch the surface. Advantageous features of the product is that it is sold in a single pack strippable protec-25 tive coating. It has a thixotropic property which allows coating of 2023 the substrate when it is oriented,at varying angles. It dries rapidly in air. It is hydrophobic and thus can be used on wet surfaces. It has a corrosion inhibiting property. It has non-staining flexibility, chemical resistance and forms a moisture barrier.

In the following Table IV there are listed properties of the film formed by the composition and method of the present invention as compared to known vinyl and nitrocellulose type strippable coatings showing the advantages of the present invention.

The modifiers in the composition contribute to the physical properties of the coating but do not chemically react with the polymer. They assist in improving the tensile or cohesive strength of the coating, increasing the coatings resistance to elevated temperature and lower the melt viscosity.

When the proportion of polymer relative to modifier is at its optimum the following properties are enhanced: (a) inertness to chemical attacks, (b) a balance of cohesive and adhesive properties, (c) non-stainability, (d) good flexibility, and, (e) lower cost.

Where there is a higher relative concentration of modifiers there is a decrease in chemical resistance, an increase in brittleness and hardness, an improvement of adhesion over cohesion, increased yellowing 202379 - ii - due to weathering and increased cost. All of these factors have to be balanced in selecting the proportion of modifier to be employed.

Claims (28)

202379 - 12 - TABLE IV Present Invention Vinyl Type Nitrocellulose Single unprimed coating Single & more primed coating Single primed coating Faster air drying Fast air/bake dry as vinyl type Flexibility with hardness Poor flexibility/medium hard No flexibility/ hard Nonstaining Stai ni ng Stai ni ng Wider range of adhesion of substrates (metal, glass, wood, plastics, insulation materials) Wide range Limited by solvents Narrow range Better chemical resistance, even at thin build coating Good chemical resistance Poor Good stability To light & heat degradati on Poor stability Poor stability Good coverage per litre Poor coverage per litre Good coverage per litre Non toxic (after drying) Non toxic in small amounts Toxic in quantity Toxi c Thixotropic (Gel to cover corners) Not thixotropic Not thixotropic Solvent wipe to strip off easily Peel off Solvent soak to strip off Price low High Medium Spray/brush/di p Spray/brush Spray/brush - 13 - 202379 VJC (>!Luvw The CI aims naf-i fling Tho tn"pntinn flra As Eollowo1-

1. A dry mix composition capable of forming a thixotropic solution in an organic solvent, the composition comprising:

Component % By Weight of Composition

An Atactic Polypropylene of Formula I

(as herein defined) 5-80

Anti-oxidant Up to 5

Modi fi er Up to 70

Filler Up to 80

2. A composition as claimed in Claim 1, wherein said antioxidant is a heat stabiliser or other known oxidation inhibitor.

3. A composition as claimed in claim 2 wherein said heat stabiliser is di-tertiary-butyl p-cresol.

4. A composition as claimed in Claim 1, 2 or 3 ,wherein said ' modifier is a resin, rubber elastomer or wax.

5. A composition as claimed in Claim 4, wherein said resin is an aliphatic hydrocarbon selected from the group consisting of ethylene vinyl acetate of low vinyl acetate content, ethylene vinyl ester of low vinyl ester content, polyethylene, polyphenylene and polybutene.

6. A composition as claimed in Claim 4 or 5, wherein said rubber elastomer is selected from the group consisting of ethylene/propylene, (ethylene/propylene diene monomer) terpolymer, natural rubber, chloro-butadiene rubber, butyl rubber and styrene block copolymer^..

7. A composition as claimed in Claim 4, 5 or 6, wherein" said wax /'

- 14 -

202379

is selected from the group consisting of a polyethylene wax, paraffin and a microcrystal1ine wax.

8- A composition as claimed in Claim 1f 2 or 3 . wherein said modifier is tall oil rosin, polyterpene or wood rosin, pentaerythrite ester, methylstyrene vinyl toluene copolymer or hydrated colophonium.

9- A composition as claimed in any one of the preceding claims, wherein said filler is selected from the group consisting of barium sulphate, chalk, lime, quartz, asbestos or synthetic fibres, talc and mixtures thereof.

10. A composition as claimed in any one of the preceding claims,

wherein said composition includes colour pigments* - - £t

11. A composition as claimed in claim 10 wherein said colour pigments are a dye comprising inorganic pigments.

12. A composition as claimed in any one of the preceding claims, wherein there is present 30 to 50% by weight of said atactic polypropylene of Formula I.

13. A solution of the composition as claimed in any one of the preceding claims in an organic solvent.

14. A solution as claimed in Claim .13 wherein said solvent is a mixture of organic solvents of relative evaporation five times faster than toluene.

15. A solution as claimed in Claim 13 or Claim 14 wherein said solvent comprises aromatic, aliphatic, cycloaliphatic or chlorinated hydrocarbons.

16. A solution as claimed in any one of Claims 13, 14 and 15

- 15 -

2.02379

wherein said solution has a solute concentratioTi of 5 to 30% by weight of the solution.

17. A solution as claimed in any one of Claims 13, 14 and 15

wherein said solution has a solute concentration of 5% by weight of the solution.

18- A solution as claimed in any one of Claims 13, 14 and 15

wherein said solution has a solute concentration of 30% by weight of the solution.

19. A solution as claimed in any one of Claims 13 to 18 wherein said solution is thixotropic.

20. A solution having the following composition:

Component % by Weight of Solution

An Atactic Polypropylene 5-50 of Formula I

(as herein described)

Gum Rosin Modifier 0-5

Calcium Carbonate 0-15

Di-tertiary-butyl p-cresol 0.1

2:1 Hexane/Toluene Blend balance

21.] A solution having a composition substantially as herein described with reference to example I or example H.

22. A method of protecting non-porous surfaces which comprises applying thereto a solution as claimed in any one of Claims 13 to 21 and allowing the solvent to evaporate to thereby form a protective

202379

- 16 -

coating.

23. A method as claimed in Claim 22 wherein said solution is allowed to dry for 5 to 10 minutes at 20°C after application.

24. A method as claimed in Claim 22 or 23 wherein said solution is applied to said surface at a coverage rate of 15 to 25 m^ per litre.

25. A method as claimed in any one of Claims ,22' to 24,wherein said method includes the additional step of wiping said coating from a so-coated substrate using said solvent when protection is no longer required.

25. A composition substantially as herein described with reference to Example I or Example II.

27. A solution with a composition as claimed in any one of Claims 1 to 12 in a petroleum solvent substantially as herein described with reference to any one some or all of the examples.

28. A method of protecting non-porous surfaces substantially as herein described with reference to any one of Examples III, IV and V.

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