US2970079A - Surface coated impregnated waterleaf - Google Patents

Description

Jan. 31, 1961 J. A. KLACSMANN 2,970,079

SURFACE COATED IMPREGNATED WATERLEAF Filed May 22, 1956 SURFACE COATING CONSISTING ESSENTIALLY OF A PHENOL- FORMALDEHYDE RESIN AND POLYMER REACTION PRODUCT OF ACYRLONITRILE, AN ALPHA OLEFINIC CARBOXYLIC ACID AND AN ESTER OF ALPHA OLEFINIC CARBOXYLIC ACID.

WEB OF POLYACRYLONITRILE FIBERS IMPREGNATED WITH A POLYMERIC REACTION PRODUCT OF ACRYLONITRILE, AN ALPHA-OLEFINIC CARBOXYLIC ACID AND AN ESTER OF ALPHA-OLEFINIC CARBOXYLIC ACID.

INVENTOR JOHN ANTHONY KLACSMANN BY @YM AGENT United States Patent 6 SURFACE COATED HVIPREGNATED WATERLEAF John Anthony Klacsmann, Newburgh, N.Y., assignor to E. I. du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware Filed May 22, 1956, Ser. No. 586,364

1 Claim. (Cl. 162-164) This invention relates to a novel article of manufacture and processes of making same. More particularly, it is related to a sheet or web of non-woven fibers having a binder of polymeric material distributed throughout.

This case is a continuation-in-part of my copending application Serial No. 531,247, filed August 29, 1955, which is in turn a continuation-in-part of Serial No. 523,605, filed July 21, 1955.

Both natural and synthetic fibers have been formed into batts or webs and then impregnated with various resinous materials which serve as a binder for the fibers. Such products are not entirely satisfactory in certain fields Where high mechanical strength, abrasion resistance, electrical resistance and resistance to greases, oils, and organic liquid solvents are desired, such as, e.g., leather replacement, papers, structural elements, bearing seals and slot liners for motors and generators.

It is an object of this invention to provide a web of fibers bound together with an organic solvent-resistant polymeric material. A further object is to provide a paper-like pellicle of a fibrous mass bound together with an organic solvent resistant polymer. A still further object is to provide a leather-like product comprising a web of polyacrylonitrile fibers bound together with a polymeric material introduced into the web as an aqueous suspension. Other objects include processes for preparing sheet materials ranging from paper-like products to leather-like products.

These and other important objects are accomplished by impregnating a web of polyacrylonitrile fibers with an aqueous dispersion of the polymeric reaction product of (A) acrylonitrile, (B) an alpha-olefinic carboxylic acid such as, e.g., acrylic acid, methacrylic acid, ethacrylic acid, phenyl acrylic acid, crotonic acid, maleic acid, itaconic acid and glutaconic acid and (C) an ester of one or more of the above mentioned (B) acids with a saturated aliphatic monohydric alcohol having 1 to 12 carbon atoms. More specific objects are accomplished by surface coating the impregnated webs with a composition comprising the above described polymeric reaction product with or without other modifying resins.

By varying the composition of the copolymer impregnant as well as the ratio of binder to fiber and the amount of heat and pressure applied to the impregnated webs, it is possible to obtain products varying in properties by varying the weight ratio of acrylonitrile to the ester of alpha-olefinic carboxylic acid from 30:70 to 60:40.

The combined acrylonitrile and alpha-olefinic ester comprises from 85% to 98.5% and the alpha-olefinic carboxylic acid comprises 15% to 1.5% of the monomer mixture from which the polymer is derived. The percentage figures are on a weight basis.

The acrylonitrile/alpha-olefinic ester ratio of the copolymer controls or determines the mechanical strength, solvent resistance, outdoor durability and flexibility of the finished product. The alpha-olefinic carboxyl'c rcid content of the copolymer stabilizes the dispersion against coagulation and aids in increasing solvent resistance and in adhering the copolymer to other materials. The ester of the alpha-olefinic carboxylic acid also aids in the coalescence of the polymer particles.

The weight ratio of fiber to hinder may vary over a rather wide range, depending on the polymer composition, i.e., the weight ratio of binder to fiber can vary from 121.5 to 1:19.

In the case of polymers useful for still articles when using the lower limits of the acrylonitrile component of the copolymer, the alkyl group of the ester of the alphaolefinic carboxylic acid is preferably derived from a monohydric alcohol having v3 to 8 carbon atoms. When using the upper limits of the acrylonitrile content of the copolymer, it is preferable to use a higher alkyl group on the ester, such as, e.g., an 8-12 carbon atom alkyl group. The esters derived from methyl and ethyl alcohol while useful tend to impart brittleness to the copolymer.

For the more flexible articles, when using the upper limits for the acrylonitrile content of the copolymer it is preferable to use an alkyl ester derived from monohydric alcohols having 8-12 carbon atoms. I

For more supple paper using the lower acrylonitrile content and the upper content of the ester of alphaolefinic carboxylic acid, it is preferable to use the esters derived from monohydric alcohols having 4-8 carbon atoms. It is also possible to use a blend of esters derived from alcohols having an average carbon length of 4-8. In general, for flexible polymers the higher the acrylonitrile content of the copolymer the greater the number of carbon atoms in the alcohol from which the esters are derived and vice versa.

The drawing is a side view illustration of theproduct of this invention showing a waterleaf impregnated throughout with a polymeric binder and a surface coating of a polymeric composition.

The following specific example represents the best mode contemplated for carrying out the invention which is given by way of illustration and not limitation. The parts and percentage figures are expressed on a weight basis unless stated otherwise.

Example A dry paper sheet was prepared from V4" staple 3 denier polyacrylonitrile fibers by preparing a .2% by weight fibrous slurry in water in the'manner well known to those skilled in the art of paper making. The-aqueous slurry was poured on a paper making screen and the water was drained through the screen leaving a matted fibrous water leaf deposited thereon. The wet water leaf was pressed between two smooth rubber covered pressure rolls to remove excess water and smooth both surfaces. The water leaf was dried then impregnated with an aqueous resinous impregnating dispersion prepared from the following components:

Parts by wt. Polymerizale monomers:

Acrylonitrile 35.00 Butyl acrylate 60.00 Methacrylic acid 5.0

Polymerization initiator:

The excess composition was allowed to drain from the water leaf and thenpressed'between two smooth rubber lites BR.15,100) 3.0 28.%-ammonium hydroxide 0.5 Water. 34.8

The: coated paperwas driedafter each dip coat by forced drying at 250 F. The paper was passed through the dip bath at a rate of l yardper minute. The surface coating onthe paper was heat cured by passing between heated revolvingsteel belts under 50-pisi. at" 340 F. for a dwell of three minutes.

The finished product had'the following'weiglitspecifications andphysical properties:

Weightspecifications: v

Total 4.50 oz./s q. yd. Weight of fiber 2. l8{oz./sq. yd. Weight polymer-in paper beiore'ceating .32 ozJsq. yd. I Weight'coating on paper. 2;00'oz./sq:yd'. Total weight of polymer.- 2.32 oa/sg: yd-.i Total weight of fiber 2.18 oZ./sq.1yd. Physical properties:

Dielectric strength 650-volts/mil;-thiekness.-

Tensile strength (strip 1 wide)- Machine direction Trans-machine direction Crease tensile strength (strip 1 W1 Machine direction Trans-machine direction; 25 lbs; at crease. Elmendorf tear strength- Machine direction -l 15 scale readings.

Trans-machine direction scale readings.

Thecoated paper described above is particularly use fulias an electrical insulation intthepresence 'of a hydro-" carbonlubricating-oil.and a refrigerantof the class con sisting of chloroalkanes, chlorofluoroalkanesandabromoalkanes. There is a tendency for objectionable copper plating to occur in some refrigeration systems when there is :used therein refrigerants.of-therclassvset forth'above/ The" product of the above: described I example; com prising polyacrylonit-rilel fibers, abinder and" a :sur facecoating containing a polymer derived from acrylonitrile is very efiective'tomateiially inhibit or delay such objectionable copperplating: if the: refrigerant and the oil are brought'a'into contact therewith OOHtiHHOUSlYTOII intermittently at frequent intervals: during; suchopera tions.: The precise mechanism through. which such-polymericmateiialsso function is not known.

Fora more'det'ailed descripti'ohof the preparation of an aqueous copolymer impregnating dispersions of this invention, reference is made to copending application Serial No. 369,890, filed July 23, 1953, by James J. Sanderson.

While there are above disclosed but a limited numberof embodiments of the structure,processandproduct of"tlfeiiiveiition herein presented; it is possible to pro duoe still otherembodiments without departing fro'mthe inventive"concept'here'in disclosedpa'n'd it is'de'sird therefore that only such limitations be imposd oh-'the"appended claimasare'stated therein; orrequired by the prior art. N v

The embodiments'ofthe invention-in which an exclusive property or privilege is claimed are defined as follows.

I claim: I

A coated water-leaf comprising a sheet of polyacrylonitrilefibers uniformly impregnated throughout with a binder comprising the polymeric reaction product of a mixture of monomerscomprising (A) acrylonit rile, (B) an alphaolefiiiic carboxylic acid selected fromthe class; consisting of acrylic, methacrylic, ethacrylic, phenyl acrylic; crotonic, itaconic, glutaconic, and maleic; and ('C an ester of said alpha-olefinic carboxylic acids and a-saturated aliphaticmo'nohydric alcoholhaving l-12 carbon atoms; the weight ratio of (A) to (C) b eingiwithin the range 30570 to :40, and (B)' beingfpresent in an amount corresponding to 1.5% to 15 %*ofthe total weight of said monomer mixture, said impregnated'sheet surface coated with a composition consistingessentially-of saidfpolymeric reaction product and a phenol-formaldehyde resin.

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