US1790839A - op berlin - Google Patents

Description

Patented Feb. '3; 1931 UNITED STATES PATENT OFFICE .GEORGE A. RICHTER; OF BERLIN, NEW HAMPSHIRE, ASSIGNOR '10 BROWN COMPANY,

OF BERLIN, NEW HAMPSHIRE, A CORPORATION OF MAINE I PULP WEB OF HIGH ABSORPTIVITY A'ND METHOD OI MAKING SAME No Drawing.. I Application filed June 1,

- In the manufacture of impregnated products using sheeted fibrous material as the base or foundation which is being impregnated, it is-frequently desired that the base be of high absorptivity and so capable of absorbing a large amount of impregnating mateweb, it is desirable that the web be capable;

of absorbing sufficient asphalt, wax,-or other waterproofing material to render the fibrous base resistant to the deteriorating effects of moisture and weathering.-

It has been found that if cellulose pulp is felted into a web on a paper machine and dewatered and dried without the application.

of substantial pressures, the resulting web is highly absorptive. be utilized to advantage especially when the pulp used as a raw material is of a highly absorbent character, such as cotton or rag fiber, or wood pul cellulose content n carrying out a method such as described, the pulp employed as a raw material ispreferably felted in unbeaten or li htly beaten condition as beating tends to reduce the size of the fibers of the pulp and results in a web of closer or denser formation and lower absorptivity. When substantially unbeaten pulp is felted and dried on a papermaking machine without being subjected to substantial pressures, the resulting web is composed. of fibers of original length in a loosely felted substantially uncompacted condition. A pulp web thusmade, while highly absorptive has the disadvantage of being dif- .ficult to handle without tearing. -This trouble renders the absorptive web unsuitable for use. as a raw material in a process which places it under stress, as it tends to break even under comparatively low tensions.

50 I have found that if a relatively small Such a method may refined to high alpha 1928. Serial No. 282,277.

amount of gelatinized cellulose is mixed with the unbeaten pulp prior to its felting and the mixture sheeted and dried, as hereinbefore described, the resulting web is materially improved in its physical characteristics while its absorbency is substantially unafiected. The gelatinized "cellulose apparently bonds together the loosely felted substantially uncompacted fibers of original lengthwithout, however, materially afiecting its absorptivity and penetrability. By forming a web in accordance withthe present invention, it may be drawn through a bath of liquid saturant satisfactorily, the resulting product containing a maximum amount of saturant due to its high absorptive character. For instance, by passing the web through a rubber-containing bath, e. g; rubber benzine solution, rubber latex or aqueous dispersion of rubber, a product having a very high rubber content and possessing excellent characteristics for use as an artificial leather .is produced. The

strengthened webalso lends itself well to coating or saturation with thermoplastic materials, such as asphalt or waxes such as Montan and carnauba, with'varnishes or lacquers of the nitrocellulose type, and with other materials. p

In practicing the method of the present invention, pulp of any suitable origin, for instance sulphite or kraft pulp, may be employed as a raw material, but if av high grade absorbent web suitable for use as a filter sheetor medical gauze is desired, cotton or rag fiber or wood fiber which has been refined to high alpha cellulose content is preferably employed. The pulp is-preferably subjected to little beating, as itis desired to preserve the original length of the fibers and toproduce a web of open or loose formation with such fibers. In some cases it is preferable to employ only the long fiber portion of the pulp as this portion not only results in a sheet of high strength and tear resistance, but also of very great absorptivity. The separation of the long fiber portion from the rest of the pulp may be efiected as by passing the pulpthrough an apparatus of the type described i only the long fiber portion is especially advantageous in the case of a high grade pulp, such as cotton fiber or wood fiber refined to high alpha cellulose content, intended for the manufacture of a web of high purity and permanence, and suitable for use as a filter sheet or in making surgical dressings. It has been found that the long fiber portion of pulp of this character is much whiter and cleaner high alpha cellulose content, beginning with no gel and then mixing therewith 5%, 8%

and 12% gel based on the air-dry weight of pulp.

N o 5 per- 8 per- 12 pergel cent gel cent gel cent gel Basic weight (24X36480) 49.-6 48. 8 48. 0 48. 8 Thickness (in inches); 0. 0210 0.0193 0. 0176 0. 0177 Compactncss 24 25 27 28 Strength (Mullen) 24 26 31 Tear resistance (machine direction) 143 147 183 193 Tear resistance (across web) 141 148 165 175 Stretch (machine direction). 8. 20 9. 40 9. 80 11. 30 Stretch (across web) 5.95 6.25 10.90 10. 90 Breaking length (machine direction) 309 820 1085 1260 Breaking length (across web). 214 530 800 914 Absorbency (water 5 min.) 580 530 520 530 Breaking length is the length of paper which it freely suspended would break as a result of its own weight.

All the webs were made substantially under the same conditions, the stock furnish being run off on a paper machine into a web which was dewatered and dried without being subjected to substantial pressures. The comparative values given, while associated with the use of a particular type of fiber as a raw material, are illustrative to a greater -or less extent of the comparative values obtained when using other types of fibers.

The compactness value, hereinbefore given,

was obtained by dividing the basic weight by the thickness and multiplying by the factor 10*. The vabsorptivity was ascertained by noting the water crawl up a strip, the values given denoting hundredths inches crawl on the strip in 5 minutes. It is to be observed. that the strength, tear'resistance and breaking length of the web. is materially higher when gel is employed in the pulp furnish. The improvement in these characteristics is of much more significance than the --values indicate, for it means satisfactory use of the web in many processes in which it could not heretofore be employed as a raw material served that 'the improvement in physical characteristics of the web was effected with but little change in its absorptivity.

Having thus described certain. embodiments of this invention, it is evident to those skilled in the art that various changes or modifications might be made therein without departing from the spirit or scope of the invention as set forth in the appended claims.

I claim 1. A cellulose pulp web comprising gelatinized cellulose and loosely felted substantially uncompacted fibers in an unbeaten condition.

2. A cellulose pulp Web comprising gelatinized cellulose and loosely felted substantially uncompacted fibers of original length and of high alpha cellulose content.

3. A cellulose pulp web comprising loosely felted substantially uncompacted fibers of original length and of high alpha cellulose centent, bonded together with a comparatively small amount of gelatinized cellulose.

4. A cellulose pulp web comprisiu the long fiber portion of a pulp in a loosely elted and substantially uncompacted condition and bonded. together with gelatinized cellulose.

5. A cellulose pulp web comprising the unbeaten long fiber portion of a pulp of high alpha cellulose content in a loosely felted and substantially uncompacted condition and bonded together with a comparatively small amount of gelatinized cellulose.

6. A method which comprises mixing unbeaten cellulose pulp with gelatinized cellulose, and forming themixture into a loosely felted uncompacted web.

7. A method which comprises mixing substantially unbeaten cellulose pulp with gelatinized cellulose, andfelt-ing and drying the mixture without subjectingit to substantial comparatively small amount of gelatinized cellulose with unbeaten pulp freed from its short fiber portion, including fibrillae, fiber fragments and colloidal cellulose, and forming the mixture into a loosely felted-uncompacted web.

- 10. A cellulose pulp web comprising loosely felted, substantially uncompacted fibersinan unbeaten condition, bonded together by mechanically gelatinized cellulose.

In testimony 'whereof. I have afiixed, my

signature. r 1

GEORGE AQRI CHTER.