JPH026686A - Poly (vinyl alcohol-vinylamine) copolymer for paper product having improved wet compression strength - Google Patents

Abstract

PURPOSE: To produce a paper having increased moist compressive strength by adding special cationic poly(vinyl acetate-vinylamine) to an aqueous slurry of cellulose fibers and making a sheet from the slurry. CONSTITUTION: Cationic poly(vinyl acetate-vinylamine) containing vinyl acetate units, at least 90 mol% of which have been converted into vinyl alcohol by hydrolysis and 1-50 mol% vinylamine units is added to an aqueous slurry of cellulose fibers by 0.1-3 wt.% of the amount of the cellulose fibers a sheet is made from the slurry.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the production of paper and paperboard by depositing wood aluminum from aqueous slurries, and more particularly to improvements in the wet compressive strength of such paper products.

paper, paperboard and similar water-twisted paper webs (hereinafter “
In the production of "paper"), a cellulose fiber slurry containing rosin size and inorganic components (fillers) according to the desired product is deposited and discharged onto a continuously moving wire screen. In the process, the free water passes through a paper cooler and the web is further processed to obtain the desired paper product.

Paperboard cartons that are stored or stacked under conditions of high humidity (90+%) absorb high levels of moisture, approximately 14-17%. This absorbed moisture can cause the cartons to buckle, especially near the bottom of the stack, or cause the stack to tip over and damage the contents.

One solution to this problem is to increase the weight of the boxboard product, but packagers prefer to use stronger cartons at lighter weights.

Therefore, there is a need for a means to improve the wet compressive strength of paper products.

U.S. Pat. No. 3,597,314 states that 0.05
Add ~4% of a water-soluble polymer composed of units derived from N-vinyl-N-methylformamyl containing essentially 60-100% of the formic acid groups of the polymer degraded by acid hydrolysis. A method for dewatering an aqueous cellulose fiber suspension, possibly in the manufacture of paper, is disclosed.

H, Il (, EsPY's "TAPPI Proceed
ings (1983)” pp. 191-195 (Pap
Paper Makers Conference) discloses that a combination of carboxymethyl cellulose (CMC) and poly(aminoamyl) shrimp chlorohydrin (PAE) wet strength resins provides improved wet and dry strength over the PAE resin alone.

The present invention provides a means to increase the wet compressive strength of paper products made by depositing cellulose fibers from an aqueous slurry. The improvement is that an aqueous slurry of cellulose fibers comprises an effective amount of essentially poly(vinyl acetate-vinylamide), preferably carboxymethyl cellulose, in the ratio of 0.5 to 5 parts by weight of cationic polymer for every part of anionic polymer. It consists in adding a wet compressive strength additive consisting of a combination of anionic polymers such as. The vinyl of poly(vinyl acetate-vinyl amide) The acetate units are at least 75 mol %, preferably 90 mol %, hydrolyzed to vinyl alcohol units, and the vinyl amide P units are hydrolyzed to 1 to 50 mol %. This gives a polymer having mol % of vinylamine units.

In addition to improving the wet compressive strength of paper products, such paper products can be more easily modified because their wet tensile strength is lower than that typically achieved by the use of PAE wet strength resins. Can be repulped.

Measures to improve the wet compressive strength of papermaking have been incorporated into the wet-en-P stage of the papermaking process.

The amount of additive composition effective to increase the wet compressive strength of the paper product, e.g. 0.1 to 3 based on cellulose fibers
% by weight is added to an aqueous slurry of cellulosic fibers such as wood pulp. The added composition is essentially poly(
Vinyl alcohol-vinyl amine) CP(VOH-V
Am), ), preferably in combination with carboxymethyl cellulose (CMC). The most preferred compositions contain 0% per part of anionic polymer.
．． 5 to 5 parts p(voa-vAm), preferably about 2 parts p(voH-vAm) per part of anionic polymer.
).

P(VOH-VAm) has at least 75 mol%, preferably 90+ mol% of its vinyl acetate units hydrolyzed to vinyl alcohol units, and most preferably about 990 mol% hydrolyzed. poly(vinyl acetate-vinylamide), which is completely hydrolyzed. The amount of vinylamine P units in the hydrolyzable polymer is at least 1 mol%, preferably from 3 to 30%, based on the total polymer, depending on the molar ratio of poly(vinyl acetate) to poly(vinylamide)K. mole %, and most preferably 3
The amount should be sufficient to provide ˜12 mole percent vinylamine units. Thus, P(VOH
-VAIII) component is non-hydrolyzed vinylamide)%
and/or an amount of vinyl acetate units.

Suitable P (VOH-VAIII) polymers are about 1 to 5
Contains 0 mol%, preferably 3 to 30 mol% vinylamine units, the remainder being vinyl alcohol units,
and if the polymer is not completely hydrolyzed it will contain amounts of vinylamide and vinyl acetate units. The molecular weight of p(voH-vAm) is 000 to 300,
000, preferably within the range of 10,000 to 100,000.

p(voH-vAm) suitable for use in the present invention
) is the same as the well-known method of producing polyvinyl acetate and hydrolyzing it to polyvinyl alcohol, except that it involves the incorporation of vinylamine) 11 monomer into the polymerization reaction. This is the way to do it. Vinylamine P monomer is vinylacetamyl
Alternatively, it may preferably be vinylformamide, especially N-vinylformamide.

Representative references for producing p(voa-vAm) include W, M. Brouwer et al., J. Polym.
, Sci, , Polym.

Chem, Ed, 22, 2353 (1984
year) and C, J.

Eur of Bloys van Treslong et al.
Polym, J., 19 (2).

131-4 (1983).

A preferred method for preparing p(voH-vAm) is described in 'Method For Pr
eparingPoly (vinylalcohol
) -Co -Po1y (vinylamine)
Viaa Two-Phase Process'
Disclosed in the application entitled.

In addition to P(VOH-VAm), the wet strength additive composition preferably contains anionic polymers such as anionic starch, carboxymethyl guar, polyacrylic acid,
% partially hydrolyzed polyacrylamide, most preferably CMC.

The degree of carboxymethyl substitution of CMC is 0.2-1.2
The molecular weight is within the range of io,ooo~300,
Within the range of 000.

The amount of wet strength additive composition added to the slurry of cellulosic fibers is about 0.1-3% by weight, preferably about 0.2-2% by weight, based on the fibers. P (VOH
-VAm) is added to the slurry before adding the anionic polymer. If the two components are mixed together before adding them to the slurry, a gummy mixture results. Preferably, P (VOR-VAm) and the anionic polymer are added as an aqueous solution.

P (VOH-VAm), which is cationic, is absorbed by the anionic cellulose fibers, and especially with the addition of anionic polymers, electrostatic bonds are formed to form polyelectrolyte complexes, whose stronger interfiber bonds make the fibers It is believed that the strength of the matrix is increased.

By electrostatic bonding such polyelectrolytes are produced and by reducing the susceptibility of the fibrous structure to the weakening effects of moisture, the treated paper has a high compressive force, e.g. cartons produced from such treated components Can better withstand compressive forces when stacked under conditions of humidity and high moisture content. However, the interfiber bonds can also be broken during the typical re-Ruzotization process.

Example 1 Southern pine (5outhern pi) was used for the following experiments.
The unbleached kraft pulp of
Freeness) (C8F) was beaten in tap water. Beaten. The e-Ruso was then classified (fine particles were removed) to produce 7004 final filtrate. (The purpose of classifying the Sorzo was to retain the polymer and the fines, i.e. to avoid the change-prone interaction of the fines fraction that could affect the strength properties.) The pulp was then dehydrated and
5% solids and in the presence of a small amount of preservative before being used in handsheets. It was stored in Hen P
Immediately before sheet production, the dewatered pulp was suspended in tap water at a consistency of 1.5% using a British back frame disintegrator.

It was then diluted to a 0.5% consistency and used to produce each set of handsheets equivalent to 30 tons (oven dry weight).

Several p(voa-vAm) solutions were first prepared by stirring to approximately 0.025% solids, and the suspensions were then aged in distilled water overnight at room temperature. The resulting solution was filtered through a 325 mesh sieve to remove undissolved polymer. Low viscosity CMC (D, s, = o,
7) was dissolved at 1% solids in distilled water for use in handsheets (by boiling at 95°C for 20 minutes).
did. Commercial standard PA3 (Hercules; K
ymene™) was diluted to 1% solids before adding the pulp. When containing a combination of polymers, the predetermined amount of cationic component was first stirred in a pulse for 5 minutes, then the CMC was added and stirred for an additional 5 minutes. 2.5t
The amount of pulp that is sufficient to mold one hand sheet (63 t/m2) is separated and its molding consistency is 0.
0.04% Noble & Wood mold.

Handsheets were formed on 100 mesh Monel wire, blotted onto a blotting paper stock, pressurized at 50 psig for 5 minutes, and dried on a steam drum at 220"F for 7 minutes. Control handsheets were Molded from pulp treated with pulp and additives as found in Tables 1 and 2. Basis weight, wet tensile strength, and dry and wet after setting conditions of 50% volume and 75″F Tests were conducted for compressive strength. Wet compressive strength and wet tensile strength modulus were determined by dividing the value of the treated sheet by the value of the untreated control. Table 1 shows the amount of cationic and anionic additives in the fiber slurry and the pH of 7 to 9.
presents performance data for paper products made from the commercial Southern Pine Selzo grade. The experiments in Table 2 used a fiber slurry that was maintained at pH 4.5 during the sheet manufacturing process by adding dilute sulfuric acid.

Blank control P(1) pAE(1); CMC(0,4) p(vaH-vAm)(1) P(VOH-VAIlIXl); CMC(0,1)P(
voH-vAm) (1); CMC(α2)p (
voH-vAm) (1); CMC(0,4)p
(voH-vAm) (1) p(voa-vAm) (1); CMC(o, 4) p(v
oH-vAmXl);cMe(o,5)p(voH-v
AUl) (1) ;CMC(t2)p (voH-v
Am) (1) p(voa-vmXl):CMC(α4)p(voH-
vAm) (o5); cuC(0,5)p(voa-
vAJnX[L5):cMc(to)p(voH-vA
m)(03):cz(15)pH4,5 62,66,43&81 6t6 7.59 567 690 1α4 5.08 0.96 1.33 1.0 15.7 22.1 63.7 67.2 64.9 62.5 7.99 8.11 7.60 '5.88 4.54 4.17 3.75 [198 66,2 62,9 6 & 4 62.4 8.03 8.79 8.74 8 .42 4.34 4.43 4.66 4.82 1.14 1.27 63゜1 a7 6&4 61.6 63.2 7.93 8.91 4.52 Age 65 4.34 4.45 1. 22 1.14 It can be seen from the data in Table 1 that the paper products of the present invention (Experiments Nos. 5-16) have superior dry and wet compressive strength and wet tensile strength than the untreated control paper products. Gave.

The combination of P(VOH-VAm) and CMC is P(V
OH-VAnn) gave a paper product that was superior to that produced using it alone. (CMC itself has little or no beneficial effect on the strength properties of the paper when added to the fiber suspension) 0.2 or 0.4% C
Addition of 1% p (voH-vAm) along with MC showed maximum or near maximum compressive strength properties.

From Table 2, it can be seen that the performance of P(VOR-VAm) in combination with CMC is somewhat lower under acidic conditions than under alkaline conditions.

The level of wet tensile strength produced by p(voa-vAm) is typically lower than that achieved using PAE wet strength resins in combination with CMC, and
It has been suggested that paper treated with H-VAm) may be more easily resolvated to achieve the desired properties.

Example 2 Repulping studies (a) blank control without additives)
, p) 14.5; (b) PAR (1%), pH 4
,5; (c) PAE (1%) and CMC (0,4
%), pH 4,5; (a) p(voa-vm)(1
%), PH4,s; (e) p(voa-vAm)
(1%), pH 7-8; and (f) p(voH
-vAm) (i%) and CMC' (0,4%), p
The experiment was conducted using various non-r sheet sets manufactured under each condition of H7-8. p (voH-vAm) is 6
% amine functionality and the molecular weight is 130.00
It was 0.

The handsheets containing p(vaH-vAm)C(d), (e) and (f)] all re-rusotized significantly better than the reference sheets) [(b) and (C)]. Handsheets molded at -7 to 8 containing P(VOH-VAm) alone or with CMC have a pH of 4.
, 5 had less dispersed fibers than P(■OH-■Am). The results of visual inspection of the diluted fiber slurry correlate with the above observations.

The combination of high dry and wet compressive strength and better repulpability obtained with the use of p(voH-vAm) therefore represents a distinct advantage over combinations containing PAE.

〔Effect of the invention〕

Paper products with improved wet compressive strength are obtained by using p(voa-vAIn) in the WetEnP stage of the papermaking process, preferably with CMC as an additive.

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Claims (1)

Claims: 1) In a method of manufacturing a paper product by depositing cellulose fibers from an aqueous slurry thereof, an aqueous slurry of cellulose fibers is comprised of an effective amount of an essentially cationic poly(vinyl acetate-vinylamine). , in which at least 90 mol% of the vinyl acetate units are hydrolyzed to vinyl alcohol, and the wet compressive strength of the paper product is increased by adding an additive containing from 1 to 50 mol% vinylamine units. The above method, characterized in that the method comprises: 2) A method according to claim 1, wherein the copolymer contains 3 to 30 mole % vinylamine units. 3) The method of claim 1, wherein about 99+ mole percent of the vinyl acetate units of the copolymer are hydrolyzed to vinyl alcohol units. 4) An effective amount of 0.5 to 5 parts by weight of poly(vinyl acetate) per part of an essentially anionic polymer is added to an aqueous slurry of cellulose fibers in a process for making paper products by depositing cellulose fibers from an aqueous slurry thereof. - vinylamide), at least 90 mol% of whose vinyl acetate units are hydrolyzed, and the vinylamide units are hydrolyzed such that the polymer has 1 to 50 mol% vinylamine units; A method as above characterized in that a certain wet compressive strength additive is added. 5) A method according to claim 4, wherein the anionic polymer is anionic starch, carboxymethyl guar, carboxymethyl cellulose, polyacrylic acid or partially hydrolyzed polyacrylamide. 6) The method according to claim 4, wherein the anionic polymer is carboxymethyl cellulose. 7) The method of claim 4, wherein the vinyl acetate units are hydrolyzed to about 99+ mole percent to vinyl alcohol units. 8) A method according to claim 4, wherein the cationic polymer has 3 to 30 mole % vinylamine units. 9) The method of claim 4, wherein the additive composition consists essentially of about 2 parts poly(vinyl acetate-vinylamide) per part anionic polymer. 10) 0.1 to 3% by weight, based on fiber, essentially 0.5% per part of carboxymethyl cellulose in an aqueous slurry of cellulose fibers in a process for making paper products by depositing cellulose fibers from an aqueous slurry thereof.
~5 parts by weight of poly(vinyl acetate-vinylamide)
consisting of at least 90 vinyl acetate units thereof
The above characterized in that a wet compressive strength additive is added, of which mol % is hydrolyzed and the vinylamide units are such that the polymer is from 1 to 50 mol % vinylamine units. Method. 11) A paper product produced according to the method of claim 1. 12) A paper product produced according to the method of claim 2. 13) A paper product produced according to the method of claim 3. 14) A paper product produced according to the method of claim 4. 15) A paper product produced according to the method of claim 5. 16) A paper product produced according to the method of claim 6. 17) A paper product produced according to the method of claim 7. 18) A paper product produced according to the method of claim 8. 19) A paper product produced according to the method of claim 9. 20) A paper product produced according to the method of claim 10.