US 3486970 A
Description (OCR text may contain errors)
United States Patent Int. (:1. min /02, 5/12 US. Cl. 162-157 3 Claims ABSTRACT OF THE DISCLOSURE Polyacrylonitrile fiber paper having transparent embossings on the basis of fibrillated polyacrylonitrile fibers containing at least 80% by weight of bound acrylonitrile, prepared by embossing a paper sheet as just described at a temperature just below the softening point of the polyacrylonitrile polymer.
This invention is concerned with patterned embossed polyacrylonitrile fibre papers and to a process for producing embossed polyacrylonitrile fibre papers.
It is known to emboss foils of thermoplastic synthetic resins such as polyvinyl chloride by means of a heatable embossing calender. Embossing textiles and papers made of cellulose raw material is also carried out between engraved steel rollers which may be heated.
A process for the production of polyacrylonitrile fibre papers provided with transparent embossings has now been found in which paper made from polyacrylonitrile fibres containing at least 80% bound acrylonitrile are subjected to a thermal embossing operation. Polyacrylonitrile fibre paper of this kind consists of polyacrylonitrile fibres which are uncollapsed but are capable of fibrillation, and they are manufactured by known processes. The fibres are fibrillated in an aqueous suspension, for example in a beater or refiner, and worked up into papers on known types of paper machines. As acrylonitrile polymers containing at least 80% of bound acrylonitrile there are preferably used copolymers of acrylonitrile and acrylates, such as for example methyl methacrylate and methylacrylate. In addition, however, it is also possible to incorporate by polymerization other monomers such as vinyl chloride, vinylidene chloride, and ethylenically unsaturated compounds containing sulphonic acid groups or other acid groups. The process may, of course, also be carried out with a paper which consists solely of polyacrylonitrile fibres which are uncollapsed but are capable of fibrillation. Papers which have been manufactured from a mixture of uncollapsed polyacrylonitrile fibres capable of fibrillation and a proportion, amounting to 20% at the most, of fibres of regenerated cellulose (viscose) can also be subjected to a thermal embossing operation.
Embossing of the paper is carried out at temperatures just below the softening point of the polymer, and it may be carried out continuously with the aid of heated embossing rollers. On the other hand, embossings of this kind may also be produced by means of plate presses designed for embossing. An embossing roller which has a rubber roller, cotton roller or paper roller as counter roller may, for example, be used for the continuous embossing process. Surprisingly, if thermal embossing is carried out in this way, complete transparency occurs in "ice the embossed areas and sharply outlined figures or images are obtained whereas the paper not affected by the embossing process retains its opaque character. The embossing is carried out with roller temperatures between 190 and 240 0., depending on the polymer and the embossing pressure. The nature of the transparency also depends on the hardness of the counter roller. The process may also be carried out with colored papers. To color these papers, a process which is carried out by known methods, it is preferred to use basic dyestuffs, for example of the triphenyhnethane or phthalocyanine type.
The papers manufactured in accordance with the above process from uncollapsed polyacrylonitrile fibres capable of fibrillation may be used as a decorative or covering material, e.g. for lampshades, wall panels or curtaining or blinds.
The invention will now be described with reference to the following examples which are given by way of illustration only:
EXAMPLE 1 Undisintegrated pure polyacrylonitrile fibres capable of fibrillation, 6 mm. in length and having a titre of 2 den. were fibrillated in a laboratory beater and worked up in known manner on an experimental Fourdrinier machine of the Kammerer type. The finished paper had a tear length of 5120 m. and relative wet strength of 71.6%. It was conveyed through an embossing calender heated to 205 C. which was equipped with a cotton roller as counter roller. The embossing obtained on the paper by this process was glass clear whereas the unembossed areas retained the original properties and optical qualities.
EXAMPLE 2 A paper manufactured from Undisintegrated polyacrylonitrile fibres which are capable of fibrillation and in which acidic groups of ethylenically unsaturated compounds had been incorporated by polymerization was subjected to an embossing process as described in Example 1.
EXAMPLE 3 Undisintegrated polyacrylonitrile fibres capable of fibrillation, in which acidic ethylenic compounds had been incorporated by polymerization, were dyed by known processes with Astrazon Red GTL (C.I. Basic Red 18). As indicated in Example 1, the fibres were fibrillated and worked up into paper. Embossing, which was carried out with embossing rollers (heated to 196 C.), yielded colored, glass-clear sharply outlined patterns.
EXAMPLE 4 A paper consisting of a mixture of undisintegrated polyacrylonitrile fibres capable of fibrillation and 20% regenerated fibres produced by the cuprammonium process was subjected to a thermal embossing process as described in Example 1. The embossed patterns appeared glass-clear on the paper.
What We claim is:
1. An embossed polyacrylonitrile fibre paper consisting of fibrillated polyacrylonitrile fibers containing at least 80% by weight of bound acrylonitrile and having uniform transparent sharply outlined embossed areas interspersed with opaque non-embossed areas.
2. An embossed polyacrylonitrile fibre paper according to claim 1 wherein said opaque areas have the same properties and optical qualities as the paper prior to its being embossed.
3. An embossed polyacrylonitrile fibre paper accord- S. LEON BASHORE, Primary Examiner ing to claim 1 having had incorporated therein a coloring T G FERRIS Assistant Examiner agent.
References Cited U S Cl XR UNITED STATES PATENTS 5 161 13 162 117 2,689,199 9/1954 Pesce. 2,784,135 3/1957 Wooding et a1. 162-157