CA1078541A

CA1078541A - Compound for coating containing fluorocarbonpolymer and method for its manufacture

Info

Publication number: CA1078541A
Application number: CA252,779A
Authority: CA
Inventors: Toshio Yasuda
Original assignee: Individual
Current assignee: Individual
Priority date: 1975-05-19
Filing date: 1976-05-18
Publication date: 1980-05-27
Also published as: JPS5340210B2; JPS51134726A; DE2622343A1; DE2622343C2

Abstract

ABSTRACT OF THE DISCLOSURE

A new compound and its method of production composed of three elements namely a fluorocarbonpolymer, a rubber-like elastic material, and a thermoplastic or thermosetting bonding strength reinforcing resin, the resin being material which is partially or completely compatible with the rubber-like material and when dissolved in a common solvent producing a substantial and homogenous film, the composition for making the film being formulated in the proportion where the ratio by weight of the fluorocarbonpolymer to the elastic material plus the resin is in the range of 20/80 to 80/20 and the ratio by wieght of the elastic material to the resin is in the range of 95/5 to 30/70.

Description

~71~59~

The invention relates to a compound which contains a fluorocarbonpolymer and possesses rubber~like elasticity.
Additionally, the invention is concerned with a coating compound as described below and the method of manufacture of such a compound for coating the surface of any object to form a coating film thereon having the property of self-lubrication which is peculiar to fluorocarbonpolymer and having the characteristics of free deformation in elongation, bending and contraction by the effect of external force but which can be restored to its original state after the relief of such external force.
All of the fluorocarbonpolymers such as polytetrafluoroethylene (abbreviated to PTFE hereunder), tetrafluoroethylenehexafluororo,pylene copolymer (abbreviated to FEP hereunder) have self-lubrication and non-adhesive characteristics so that they are widely utilized for industrial and household uses as the fine powder of such polymers when applied on the surface of an object can be melted to produce a very slippery or non-adhesive film. However, the process of heating and melting such fluorocarbonpolymers after they are coated on the surface of the object is complicated and it is im-possible to apply heat on any object which may be deteriorated by the heating as the melting point of such polymers coated on the surface of objects are too high.
Therefore, there is also used a method of coating a compound consisting of a fine powder of fluorocarbonpolymer or a liquid dispersion of it combined with thermoplastic or a thermosetting resin on the surface of an object to constitute a slippery or non-adhesive film thereon by letting the film dry in air or at a temper-ature less than the melting point of the f:Luorocarbon~olymer to avoid deterioration of the object. For instance, U.K. Patent No.
1,018,269 dated January 26, 1966 entitled, Improvements in or Relating to Resin Compositions, specifies that a compound consisting ;785~
a low molecular weight PTFE and a thermoplastic ~r thermosetting resin can form a hard film under normal temperature and it is possible to obtain a fluorocarbon coating film with this compound not only on the surface of a metallic object but even on the surface of wood or paper which is quite liable to deteriorate from heat. It is also specified in the U.K. Patent No. 1,06~,840 dated April 12, 1967 entitled Tetrafluoroethylene/herafluoropropylene Copolymer Dispersions, that a compound consisting of FEP organosol and a thermoplastic or thermosetting resin can produce a coating film of fluorocarbonpolymer on the surface of an object by heating the coated film at a temperature lower than the melting point of the fluorocarbonpolymer.
However, it is obvious through the reports of practical tests included in the specifications of the above patent that every thermoplastic or thermosetting resin employed as the film forming material combined with fluorocarbonpolymer can adhere firmly to a hard object such as a metallic material but its film is very hard and lacks the properties of elongation and flexibility. Therefore, when the compounds as mentioned above are applied on the surface of rubber or rubber-like elastic objects and dried by normal temperature for thermoplastic resin or heat-treated by predetermined temperatures to form the surface coating film, the film will easily be cracked by bending or compressing owing to the hard film created by the film forming material and also due to the characteristics of of rubber or rubber-like elastic objects which may have been deteriorated by the heat treating of the thermosetting resin where it was used in lieu of thermoplastic resin. Rubber or rubber-like elastic material is high in friction strength so that minimizing the friction strength on the surface of rubber or rubber-like materials permits full use of its elastlcity and flexibility,The field of application of it is much extended. In order to give the self-lubrication and non-adhesi~e characteristics of fluoro-carbonpolymer to the surface of rubber or rubber-like elastic material, it has been tried for instance, to fill it with a fine powder of PTFE or FEP. It was found very difficult, however 1~

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~ ~ ;float the fine powder of PTFE or FEP to the surface o~ the rubber ; or rubber-like material due to its high in viscosit~, I-t required a mix and blend of at least 50% by weight oE fine powder o~ PTFE ~r FEP based on the total weight of the composition containing the rubber or rubber-like material in order to achieve a suitable slippery surface on it. ~he above method is not practically useful as it has a high cost of product from the use of large amounts of fluorocarbonpolymer and also will cause considerable deterioration of the original characteristics of the rubber or rubber-like material.
For the reasons mentioned above, it is impossible to make a coating film having the characteristics of slipping and flexibility of deformation on the surface of the rubber or rubber-like material without deteriorating the original nature of the base object.
The inventor of the invention has prepared several compounds consisting of a wax-like low molecular weight PTFE as being used by the said U.K. Patent No. 1,018,269 or FEP organosol as specified in the said U.K. Patent N0. 1.064,840 and soft type rubber-like elastic material polyurethane rubber or polychloroprene insolution as film forming material in lieu of thermoplastic or thermosetting `~ hard type film forming material as also being used by the above patents, Each of the compounds produced as above were coated on the surface of a rubber or rubber-like object and dried to form a film and then the characteristic of each film was investigated, The result of the investigation proved that it was possible to obtain a film having good flaxibility from films having a ratio of com-position of fluorocarbonpolymer and rubber-like elastic material in the range of 20/80 - 60/40. However, it was noted that the coating films as applied showed poor adhesion due to the nature of the objects and further it was learned that the coating films were lacking in the desired low frlction characteristic which derived from a softnes~ of the films.

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The inventor has found tha-t it is possible to produce a compound for coating the surface of an object to create a film which is self-lubricative as peculiar to fluorocarbonpolymer and which will flexibly deform itself in elongation, bending and contracting accordingly and which can restore itself to its original state after the relieving of the deformation. The method of manufacture of the compound is to add the proper ratio of a polymer as a third ingre-dient to the aforementioned two element compound which consists . .
of fluorocarbonpolymer and rubber-like elastic material. The third ingredient is a polymer which can form by itself a hard or semi-hard film with strong adhesive attachment to the object on which it is applied and which has the characteristic of compatability with the rubber-like elastic material.
The coated film formed on the surface of an object by the two element compound consisting of a fluorocarbonpolymer and a rubber-like elastic material was compared with the film of the three element compound of this invention. It was recognized that both of them have a flexibility suitable for practical use, however, - it was noted clearly that the adhesive attachment to the object and the self-lubricating capacity of the latter was far superior to that of the former.
The fluorocarbonpolymer used as a principal ingredient of the compounds relating to this invention shall be single or mixed material of polymers such as PTFE, FEP, E-TFE or a tetrafluoroethy-lene-alkylvinyleather copolymer which are mechanically pulverized into grain with diameter less than 5 mu or organosol as specified in the said U.K. Patent No. 1,064,840 and all of the above polymers have the characteristic of self-lubrication. The rubber or rubber-like elastic material to be used as an element of this invention shall be any material soluble by an organic solvent which can form an adhesive and homogenous film on the surface of the object after being coated thereon and dried.

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` Suitable adhesive and rubber-like elastic materials for the - above purpose, are synthetic rubbers such as nitrile rubber, chloro~
prene rubber and copolymer of ethylene-vinyl-acetate or polyurethane rubber, however, the best of all for this invention is the soft polyurethane rubber which excels the others in mechanical application and possesses properties of resistance to oil, heat, abrasion and has the strongest tearing strength among all kinds of elastic rubber-like materials as well as viery good adhesive attachment to a wide range of materials. It is particularly preferable to use thermoplastic polyurethane rubber which is readily soluble with organic solvent.
The material to be used for the bonding reinforcing resin (element III) of this invention mus-t be selected from materials which can be absolutely or partially soluble with the element II, . !
viz., the rubber-like elastic material. For example, when using soft polyurethane rubber as element II, the material to be combined with it as element III shall be selected from thermosetting or cold-setting epoxy resins, thermoplastic resin~ of the acrylic group, especially polymethyleacrylate, polymethylemetaacrylate and hard or semi-hard urethane which is usually called a Polyurethane Paint or a Polyurethane Binding Agent.
` In the case of using nitrile rubber of chloroprene rubber as element II, phenol resin should be used as element III. The ratio of ingredients of the coating compounds of this invention differs depending upon the purpose of use, but usually the ratio of fluorocarbonpolymer I, the rubber-like elastic material II and the adhesive strength reinforcing agent III, which is absolutely or partially soluble with II, is (I)/(II)~(III) = 20/80 - 80/20 and preferably in the range of 30/70 - 60/~0 and the ratio of composition of (II) and (III~ in the above composition shall be (II)/(III) 95/5 - 30/70 and preferably in the range of 90/10 - ~0/60.

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The coating compound relating to this invention is produced by mixing and dispersing uniformly fine powder or organosol of fluorocarbonpolymer I, rubber-like elastic material II and adhesive strength reinforcing agent III in an organic solvent and usually . .
these ingredients and the solvent can be dissolved and dispersed to an ideal condition by mixing them in a ball mill or pebble mill for minimum of 30 minutes to a maximum of 72 hours.
The compouna of this invention can form a coating film by coating the object using a normal process and the~ drying the coating in air or by heating, If needed, the object can be heated under a predetermined temperature for some hours in a range which will not deteriorate the object. The film adheres well to rubber or rubber-like high molecular weight objects and possesses a solidity not destroyed by the effect o~ elongation, bending and contraction caused by external forces. It has a low friction and non-adhesive characteristics such as are peculiar to fluorocarbonpolymers.
Quoted hereunder are several examples of practical experiments relating to this invention.
Practical Experiment No. 1.
(1) Polyurethane Rubber Solution.
Pellets (125 parts in weight) of thermoplastic urethane rubber of the polyester group as manufactured by Nippon Elastollan Industries, Ltd, with the trademark "ELASTOLLAN E185PMOO" (an adipate type thermoplastic polyurethane) having Shore Hardness 85 and 87~5 parts in weight of tetrahydrofrun (to be abbreviated as THF hereunder) are mixed and agitated in a proper agitator at normal temperature to produce a homogenous rubber solution, The viscocity of the solution at temperature 25C is 30-50 CPS,

(2) Fluorocarbon Organosol 35% by weight o~ mixed organosol solution composing of PTFE/FEP=5/95 produced by the method explained in the Japanese Patent Gazette No, SHO 48 175~8 was applied, .. r ~
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(3) Adhesive Strength ~einforcing Agent.
Polyurethane Binding Agent Solution trademarked "NIPPOLAN -2304" as manufactured by Nippon Polyurethane Industries, Ltd., was used. This binding agent is a solution of 35~ by weight of methylethylketon and its viscosity at temperature 24 C is 20,000 -40,000 CPS.

(4) The manufacture of the compound for the coating film con-taining fluorocarbon and the result of the experiment.
672 g of the soft thermoplastic polyurethane rubber solution (1), 400 g of the fluorocarbon organosol (2) and 1~0 g of "NIPPOLLAN" (3) were simultaneously put into a pot mill of 2 liter capacity and agitated to mix them for 48 hours at 110 r.p.m~ at 23 C
The mix was then taken out of the pot mill and filtered through a 120 mesh wire gauze.
Solid bod;es included in the compound were 22.75% weight.
The above solution containing fluorocarbon for coating was sprayed onto the surface of a plate in size of 50 mm x 100 mm x 2 mm made of non-adhesive PTFE and dried in air and further baked in an electric oven for 30 minutes at 150 C. Then a film of 100 mm thick-ness was peeled away from the plate and the result of the testingmade in compliance with the Japanese standard of JIS K-6301 showed good toughness and extending properties with a high percen-tage of elongation such as 380 - 420%.
The same coating compound was sprayed onto the surface of an aluminum plate and a plate of thermoplastic urethane rubber as manufactured by Mippon Elastollan Industries, Ltd~, with the trade-mark "ELASTOLLAN E195FNAT" having a Shore ~ardness 95 (size of each plate 50 mm x 100 mm x 2 mm) and they were dried in air and further baked in an electric oven for 30 minutes at 150 C. Both plates showed very good adhesion and flexibility of the coating films on them. The results of tests on coeffieient of friction, resistance against abxasion, bending, etc., of the film prepared for the above practical experiment and other films of different material are shown and compared in the list below.

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. , _. .. ._ TESTED
\ MATERIAL COMPOUND OF prrFE Nylon 6 Polyurethane TEST \ EXPERIMENT I Rubber ITEM \ Shore Hardness ... _ _ , ~ . .. ___ . .. __ ~, Coefficient of Friction 0.055-0.03 0.03 0.07 0.34 __ . __ .. ... _ . . . _ . . _I Taber System Abrasion Test (mg) 6 17 7.4 2.4 ... ~ ..... ___.__ .
Numbers of Bending more than more than Repeated Until Cracking of Film 200,000 _ _ 200,000 . ... .. ~.. ,__ , . _~_~_ _~_ Peel Off Aluminum Strength Plate 5.6 _ _ _ (25C) ~595 pOly- , _ _ .
~kg/25 mm) urethane CAN NOT
Plate PEEL OFF
~L! ~ _ ~ .... ~ .. _ _ Coefficient of Friction: Measured by Bowden, Leben Type tester with 8 mm dia. steel ball at speed of 0.23 cm/sec. for load 1 kg.
Taber Abrasion Test: Tested by Taber Abrasion Tester indicated mg value after 1,000 revolutions using an Abrastion Wheel No.
CB 17 for load 1 kg.
Numbers of Bending: Tested on a Demattia Flexing Tester by making a bend 300 times per minute from 78 mm maximum stroke to 22 mm minimum stroke at 25 C and indicated by numbers of bending until the point of time when a crack started on the specimen.
Peel Off Strength: Tested in compliance with JIS K-630L.

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Practical Experiment No. 2 (1) Polyurethane Rubber Solution.
20 parts by weight of "ELASTOLLAN E185MPOO" as specified in Practical Experiment 1 and 80 parts by weight of THF were mixed and agitated to make the solution. The viscosity of the solution at 24 C is 100-120 CPS. This solution is indicated as Urethane Rubber in the list below~
(2) Fluorocarbon Organosol, A 35% by weight mixed organosol solution of PTFE-FEP = 10/90 was produced by the method explained in the Japanese Patent Gazette No. S~O 18-17548, (3) Adhesive Strength Reinforcing Agent.

. .
Epoxy resin trademarked "ARALDITE AW106" and hardener trademarked "HV953U" both as manufactured by CIBA-GEIGY, Switzerland, are dissolved together in a mixed solvent of THF and methylisobuth-ylketon.

.. . ... _ _, ........... .. . . .
Specimen No.

--- . - ...... _ _ t~
VRETHANE RUBBER SOLUTION 320 (g) 380 (g) 450 (g) . .......... ~. . .. '' AW 106 56 ~ 45 28 ~ ~ . , __.____ ~ ............ __ ............ __ _ _ 60 50 40 , The ingredients in the above ]ist were put into a ball mill pot of 2 liter capaaity and mixed for 72 hours at ll0 r,p.m. at 25 C
and then the content was taken out of the pot and filtered through a 120 mesh metallic gauze.

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, The solid bodies contained in -the cornpound (1) was 29.29%
by weight. Each of the above solutions of fluol:ocarbon containing compound was sprayed onto the surface of non-adhesive PTFE plates with dimensions of 50 mm x 100 mm x 2 mm and dried in air and further baked in an electric oven for 10 minutes at 150 C. Each of the films of about 100 mu thickness was then peeled away from the plate and showed characteristics of great elongation and bending strength.
Each of the compounds was also sprayed on the surface of an aluminum plate and a nitrile rubber plate of Shore Hardness 70 10 and dried in air and further baked in an electric oven for 10 minutes at 150 C has shown its good adhesion and flexibility with the object.
The result of test on coefficient of friction, abrasion resistance, peel off strength and elongation of films taken from each coated plate are shown in the list below.

. ~ . . _ __ ~ ~ 1_ 2 3 _ Friction 0.04-0.0450.045-0.048 0.045-0.05 .. - _ ___ ___ ~
Taber Abrasion (mg) 12 8 6 -- -- .. ,_.. ,... - - ~ _ .
Elonqation (%) 250 290 320 _ _ . ~_ . __ Peel Off Aluminum 8.0 6.5 4 3 Strength ! __ _ ___~ __ (25C) NiStri01e 7.2 5.8 4,3 (kg/25mm) Rubber _ .
. ... _ _ Practical Experiment No. 3 100 g of chloroprene rubber (manufactured by Toyo Soda Industries, Ltd., with the trademark "SKYPRENE G-40" was dissolved in a mixed solvent consisting of 400 g of n-hexanon and 400 g of 20 ethyl-aceta-te and then to this ~;olution was added 100 g of fine powder FEP (manufac-tured by Daikin Indus-tries, Ltd. with the trade-mark "NEOFLON N-10'), 30 g of alkyl-l?henol r~sin (manufactured by Hitachi Chemical Industries, Ltd. wi.-th the trademark "~IITANOL 1501"), ... .
t ~,l -10-.

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`valac type phenol resin synthesized from alkyl phenol) and ~, g of magnesium oxide and the mix-ture was put into a ball mill pot of 2 liter capacity and operated for 48 hours at llO r.p.m. at 23 C.
The content of the ball mill pot was taken out after the completion of the operation and was then filtered through a 120 mesh metallic gauze.
The solid bodies contained in the mixed solution was 16.26 weight %.
The enamel produced as described above was sprayed on the surface of plates in size of 200 mm w. x 200 mm 1. x 2 mm t. one of which is made of vulcanized chloroprene rubber and the other is made of nitrile rubber having Shore Hardness 70 . These coated plates were dried in air and further baked in an electric oven for 30 minutes at 150 C. Either of the plates showed good adhesion of the enamel and excellent flexibility of the coated film with the object.
The result of the tests made on the coated films sprayed on the above plates is shown in the list below.

. ......... _ .. , ~ SPECIMEN FILM TAKEN FROM FILM TAKEN FROM
TEST ~ CHLOROPRENE NITRILE RUBBER
ITEM ~ P~BBER PLATE PLATE
.. ~ ~
Coefficient of Friction *
0.06 0.06 . -- .... .
NUMBERS OF BENDING more than more than (crack starting) lO,OOO lO,OOO
... .
PEEL OFF STRENGTH CAN'T PEEL AWAY CAN'T PEEL AWAY
(25 C) (kg/25 mm) . ~ . .
* Load 200 g Practical Experiment No._4 90 g of nitrile rubber (manufactured by Nihon Zeon Co., Ltd.

with trademark "E~YCAR 1042") was dissolved in a mixed solvent of 900 g of methyl-ethyl-keton and lOO g of toluene to this solution was added 130 g of fine powder PTFE (manufactured by I.C.I. I.td., Enyland, with the trademark "L-169") and 40 g of degenerated phenol resin (manu-factured by Durez Co. with ~e trademark "DUREZ 12687") and the ~ -11-~7~35~L~
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mixture was put into a ball mill pot of 2 liter Capacity and operated for 48 hours With 110 r.p.m. at 23 C.
The content waS taken out after completion of mixing operation and filtered through a 120 mesh metallic gauze.
Solid bodies contained in the compound was 23.63% by weight.
The enamel of the compound was sprayed on the surface of plates of vulcanized synthetic rubber as described in the Practical Experiment 3 and dried in air and further baked in an electric oven for 30 minutes at 150C and each of them showed very good adhesion ~-0 of the enamel to the object and excellent flexibility itself.
The results of the test made on the coated film on the panels as above are shown in the list below.

, __~ . . _ SPECIMEN FILM ON CHLORO- FILM ON NITRILE
TEST PRENE RUBBER RUBBER PLATE
ITEM PLATE
~ , ..
COEFFICIENT OF FRICTION *
0.05 0.05 ,. _ _ .. ,.._., ... ___ ___ NUMBERS OF BENDING more than more than (crack starting) 10,000 10 000 ~ ~ . ~
PEEL OFF STRENGTH
(kg/25 mm) 6.2 can't peel off ~ ~_ * Load 200 g While the invention has been described hereinabove in its preferred forms, it is desired to be protected for all forms coming within the claims hereinbelow.

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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A compound composed of three elements namely fluorocarbonpolymer (I), rubber-like elastic material (II), and thermoplastic or thermosetting bonding strength reinforcing resin (III), the resin (III) being material which is partially or completely compatible with the rubber-like material (II) and when dissolved in a common solvent producing a substantial and homogenous film, the composition for making the film being formulated in the proportion where the ratio by weight of (I)/(II) + (III) is in the range of 20/80 to 80/20 and the ratio by weight of (II)/(III) is in the range of 95/5 to 30/70.

2. A film forming composition for use in producing a coating material comprised of ingredients selected from the groups consisting of:
I. A fluorocarbonpolymer selected from the group consisting of:
Polytetrafluoroethylene, a copolymer of tetrafluoroethylenehexafluoropropylene, or a copolymer of tetrafluoroethylenealkylvinylether.
II. An elastic material selected from the group of rubbery materials consisting of: a nitrile rubber, a chloroprene rubber, a polyurethane rubber, or ethylene-vinylacetate copolymer and;
III. A bonding strength reinforcing resinous material selected from the group consisting of; an epoxy resin, an alkylphenol resin, and an acrylic resin and hard or semi-hard polyurethane.

3. The composition of claim 2 where said fluorocarbon is present in a percent by weight ratio of about 20 to about 80 percent based on the total weight of said composition, and said elastic material is present in a percent by weight ratio of about 40 to about 90 percent based on the combined weight of said thermoplastic or thermosetting bonding strength reinforcing resinous material and said elastic material.

4. The composition of claim 3 wherein said fluorocarbon is present in a percent by weight ratio of about 30 to about 60 percent by weight based on the total weight of said composition.

5, The composition of claim 4 wherein said elastic material is present in a percent by weight ratio of about 40 to about 90 percent based on the combined weight of said polymeric material and said elastic material.

6. The composition of claim 2 wherein said elastic material is a nitrile rubber and said resinous material is an alkylphenol resin.

7. The composition of claim 2 wherein said elastic material is an ethylene vinylacetate copolymer, and said resinous material is an alkylphenol resin

8. The composition of claim 2 wherein said elastic material is chloroprene rubber and said resinous material is an alkylphenol resin.

9. The composition of claim 2 wherein said elastic material is a nitrile rubber and said resinous material is polymethylacrylate.

10. The composition of claim 2 wherein said elastic material is an ethylene-vinylacetate copolymer, and said resin is polymethy-lacrylate,

11. The composition of claim 2 wherein said elastic material is a polyurethane rubber and said resinous material is a thermo-setting or cold setting epoxy resin, thermoplastic resin of acrylic group, and hard or semi-hard urethane which is usually called a polyurethane paint or polyurethane bonding agent.

12. The method of producing the composition of claim 2 that results from the mixing, dispersing, and dissolution of a finely divided powder of a fluorocarbonpolymer (I), a rubber-like elastic material (II), and a thermoplastic or thermosetting type bonding strength reinforcement resin (III) in a compatible solvent.

13. The composition of claim 11 wherein the thermoplastic resin of the acrylic group is polymethylacrylate.

14, The composition of claim 11 wherein the thermoplastic resin of the acrylic group is polymethylmethacrylate.