US1977574A - Paper bonding method and composition - Google Patents

Description

Patented Oct. 16, 1934 UNITED STATES PArsN'r OFFICE PAPER BONDING METHOD AND EOIVEQSETION No Drawing, Application November 4, 1931, Serial No. 532,978

(Claims.

This invention pertains to paper-making processes and to a new bonding material to be added to the fibers which form the paper.

We invention provides improvements in ii bonding material and in the methods or using the same and aims to eifect savings in the use of the bonding material, savings in the amount of fiber required for producing the paper and it provides various economies and advantages ld generally in paper-making processes,- as will be referred to hereinafter.

One common form of bonding material employed in paper-making is a starch gum, consisting essentially of oxidized starch made from corn, potato, tapioca or other sources of starch. Heretofore considerable difliculty has been experienced in obtaining a; satisfactory retention of the starch gum upon the paper fibers; and the gum which was not retained passed through the paper machine wires into the white water. In paper board mills, for example, where gum is used as bonding material for the liner which covers the filler, and where the white water from the liner paper web is run to waste, the starch not retained in the liner is thus wholly lost. Where, as in some mills, this white water is returned to the process it ordinarily is used as make-up water for the production of filler stock. The gum returned with the white water is not however readily retained on the fiber of the character used as filler stock in the making of paper board. Another disadvantage of unsatisfactory retention of the bonding material is that a great proportion of the short fiber stock also escapes into the white water. By the use of this new bonding material, both of these losses can be reduced and various other well known advantages which need not be set forth herein are obtained.

40 According to the present invention, the starch -gum, above referred to as one example of the bonding material is mixed preferably with sodium aluminate and aluminium sulphate and all 01' these materials run through a mill wherein they are ground to such a fineness that they will pass through a mounesh screen and preferably to such a fineness that at least eighty-five per cent of the product of the grinding operation will pass through a 200 mesh 'screen. Thoroughness of grinding is of considerable advantage toward obtaining the best results from this invention. The ground mixture is then added to the paper stock preferably subsequent to the beating operation but prior to the making of the paper web. Thus by avoiding adding the bond- (C11. tit-#331) ing material prior to the beating operation or during the beating operation there is avoided the disruptive efiects of the beating upon the bonding material. It the gunr were added in the beater the violent agitation would tend to prevent adhesion of the fiber and gum.

When the ground mixture above described is added to the fiber water, a stable flock is formed in the fiber water and is found to be a combination of aluminium hydoxide and starch gum. This effect is particularly aided by the intimate mixture which was previously formed during the grinding operation. This flocculated product then forms upon and adheres to the hydrated or partially hydrated paper stock fibers and results in w an improved bonding of the fibers in the paper web when passing over the dryers.

One notable advantage which ensues from. the use of this invention is that narrow control of the hydrogen-ion concentration of the fiber water is not so necessary as it is in prior processes. I have found that the flocks will be maintained and a very excellent retention of the bonding material is procured at any pH ranging between 3.0 and 8.5,and it will be readily perceived that the fiber water acidity can be maintained within this range quite easily. Best results are obtained between 5.0 and 1.0 pH, which is the usual operating range in most mills.

A further advantage resulting from this inven- 35 tion is that the paper produced in accordance with this invention may be dried more quickly. Hence the production of paper can be speeded up to take advantage of the decreased drying time. I also find that the sheet of paper is made more water- I proof and that there is a decrease in ink penetration. I have also found that there is a much smaller amount of short fibers and gum escaping into the white water when my invention is being practiced. I have found no difficulty in reducing by fifty per cent the amount of fiber escaping into the white water.

As one example of the preferred manner in which this invention may be practiced, the following-procedure is stated: Starch or starch gum 100 is made in the usual way and after being dried,

3 lbs. of dry chemically pure sodium aluminate and 9 lbs. of dry iron free aluminium sulphate are added to 100 lbs. of starch gum. These dry materials are mixed and then ground, preferably until about eighty-five per cent thereof will pass through a zoo mesh screen and all through a mo mesh screen. The ground mixture is then added preferably in a continuous manner to the fiber water after the beating operation has been comits pleted, whereupon the aluminium hydroxidestarch-gum-fiocks immediately form and adhere to the paper fibers. The paper is then formed from this fiber and practically all of the flocculated product is retained on the fibers, yielding a much strongerand moredurable paper when the same amount of fiber heretofore used is employed or yielding as strong a paper with a considerable reduction in the amount of fiber required.

not limited to the use of sodium aluminate and aluminium sulphate mixed with starch gum, for other materials such as sodium carbonate with alum produce an advantageous fiocculated product, and starches other than gum may be em- 'itations as to the proportions.

ployed. The proportions herein given are merely illustrative of one convenient manner of utilizing the invention and are not intended to suggest lim- The described place of addition of the bonding material is pre-' ferred, but good results may be obtained by adding 2. A bonding material for addition to fiber water in paper making processes comprising a finely ground intimate admixture of starch gum, a compound of aluminum and another ingredient capable of forming therewith when admixed in the water aluminium hydroxide, the final mixture being a dry pulverulent powder of suflicient fineness to pass through a mesh screen.

3. A bonding material for addition to fiber water in paper making processes consisting of a finely It should be understood that this invention is ground intimate admixture of one hundred parts of starch gum, three parts of dry chemically pure sodium aluminate and nine parts of dry iron free v aluminium sulphate, the final mixture being a dry pulverulent powder of sufiicient fineness to pass through a 100 mesh screen.

4. A method of improving the bonding of a paper web comprising adding to the paper stock subsequent to the beating operation and prior to the making of the web a dry finely pulverized mixture of starch gum, iron free aluminum sulphate and chemically pure sodium aluminate.

5. A method of making a bonding material for,

paper making processes comprising mixing dry starch gum together with relatively smaller quantities of dry iron free aluminum sulphate and dry chemically pure sodium aluminate and thereafter grinding the mixture to a fineness at least sufllcient to pass through a 100 mesh screen.

GEORGE E. CORSON.