FI113968B - Solution polymer stabilized with a cationic polysaccharide - Google Patents

Abstract

As additive for the production of paper and board to improve the strength of a wet web a copolymer stabilized with a cationic polysaccharide is proposed in which copolymer an acrylamide of metacrylamide, vinylic carboxyl acid and optionally other vinylic monomers are used as monomers. The wet strength of a web means the strength of a paper or board web during production at a dry solids content of 20-60%. The additive according to the invention improves, in addition to the wet strength of the web, also the surface resistance of the product. Compared to the additives of the prior art, a small relative ratio of the number of the side chains to the cationic groups is used, because a polysaccharide having a higher cationic character has been found to provide better stability.

Description

113968

Solution Polymerized Stabilization with Cationic Polysaccharide Technical Field

The invention relates to the chemistry of papermaking additives. In particular, the invention relates to a polysaccharide stabilized polymer commonly used as an additive in papermaking.

Technology background

Various papermaking additives are widely used to improve paper properties. Water-soluble additives such as polyamides, polyamide-epichlorohydrin resins, melamine resins, urea-formaldehyde resins, polyacrylamides, and preferably starch and its derivatives are used to improve the strength properties. Starch is an inexpensive raw material and naturally beneficial. The potency of the starch to improve its strength requires rather large dosages.

15

Because wood fiber is anionic in nature, native starch has a relatively low affinity for it. Because of this, starch has been chemically modified in the cationic direction. The starch is cationized by attaching to the carbohydrate backbone substituents having an ionic nitrogen-containing group, such as a primary, secondary, tertiary or quaternary ammonium group. The measure of cationicity is the use of substituted and unsubstituted *. · The ratio of glucose units in the towers, ie the degree of substitution. The cationicity may also be expressed in terms of the percentage of ionic nitrogen in the weight of the substituted starch.

The paper's strength properties need to be considered separately for wet and dry strengths.Dry strengths are generally improved by adding hydrogen bonds to the OH groups of the fiber. Such dry paper strength enhancing additives include hydrophilic, water-soluble polymers such as CMM starch, carboxymethylcellulose or synthetic polymers. These include •; ' polyacrylamides of which anionic, cationic and amphoteric are used. Their use is limited:.; : comes at a relatively high price.

:.; ·: 30: ': Wet strength is generally the strength of the finished paper when wetted, which strength; '* · Is achieved by forming covalent bonds between the fibers. This property plays a role in the manufacture of paper, for example, as filter paper or household paper, and can result from reactions between fibers and additives at a high temperature of a dry machine 113968. The second wet strength, the wet web strength during papermaking, plays a significant role in the runnability of the machine, especially when going to the drying section, since the web has until now been fully supported. This property has mainly been improved by bringing the web to a higher dry matter content in the pu-5 cross member.

In order to combine the properties of polyacrylamides and starches to improve the wet strength of paper, products have been prepared which polymerize acrylamide or methacrylamide with an unsaturated organic acid in the presence of starch. Thereby 10 starches are formed to which polymerized side chains are attached. The starch is preferably cationic, with a degree of substitution typically of 0.01 to 0.70.

Japanese Patent Application JP 2-26944 describes a polymer of acrylic or methacrylamide and methacrylic acid prepared in an aqueous solution containing a cationic polysaccharide.

15 It has been designed to improve tensile strength in addition to tensile strength. The polysaccharide has a low cationic content of 0.4% nitrogen. In one embodiment, the product is prepared by polymerization of 50-95 mol% of (meth) acrylamide and 5-50 mol% of α-β-unsaturated carboxylic acid in aqueous solution containing 40 to 90 parts by weight of a cationic polysaccharide. In another embodiment, the vinylic component to be polymerized is entirely in the form of an amide; In this reaction and after polymerization, some of the amide groups are hydrolyzed to carboxyl groups.

Japanese Patent Application JP 3-213597 seeks to reduce the bending fracture of paper or paperboard. It discloses an amphoteric papermaking additive prepared by polymerization in the presence of cationic starch from 30 to 96 mol% * '- 25 methacrylamide or acrylamide and from 4 to 50 mol% of α-β-unsaturated carboxyl. an acid or a salt thereof such that 20 to 90 parts by weight of the aqueous solution is cationic starch.

.,. The effect is said to be based on the advantageous ratio between the cationic groups of starch and the anionic groups of the carboxylic acid '·', which results in a good adsorption of the product. : to the mass.

»· ·; · '30 •'. · The number of starch side chains formed in the above-described patent applications. in relation to the number of cationic groups is high because of low cationic starch.

113968 3

Thus, additives are used in papermaking to improve the fiber-binder complex. The paper's runnability can be improved by the wet strength agents of the web. The present invention relates specifically to the wet strength of the web, i.e. the strength of the paper or board web during manufacture in the dry matter range of about 20-60%.

Description of the Invention

After intensive research, we have discovered a cationic polysaccharide-stabilized copolymer as an additive for paper and board making monomers using acrylamide or methacrylamide, vinyl carboxylic acid and optionally other vinyl monomers such as alkylaminoacrylate.

We have found that a significantly lower ratio of the number of side chains to the cationic groups in terms of strength properties compared to the prior art mentioned above is advantageous because the polysaccharide having higher cationicity gives better stability. In addition to the wet strength of the web, the additive according to the invention improves the surface strength of the product. The importance of surface strength is important for printing paper.

20: A high-cationic polysaccharide which is ready for use as an aqueous solution and does not require time-consuming cooking is used to prepare the paper and board additive according to the invention as defined in claim 1. The degree of substitution of the cationic polysaccharide is from about 0.02 to about 0.50.

Preferably, the polysaccharide used is digested starch. In addition to starch, other useful polysaccharides include, for example, dextrin, amylopectin, amylose and mannose.

In addition, vinyl monomers are used in the product of the invention.

The amount of monomers in the dry solids content of the starting materials is not more than about 30%, preferably less than 20%. The monomer component also has an amide content of at least about 95%.

113968 4

In the preparation of the product according to the invention, polymerization initiators and pH adjusting agents are used in a known manner.

The invention will now be described by way of example.

5

Example 1

Preparation of a papermaking additive according to the invention

Cationic starch (20% aqueous solution) 860.0 g 10 Water 55.0 g

Acrylic acid (80% aqueous solution) 1.2 g

Acrylamide (50% aqueous solution) 38.0 g

Tert-butyl hydroperoxide 5.3 g

Water 18.3 g Sodium metabisulfite 3.9 g

Water 18.3 g

Dry matter content 20.0%

Total amount 1000.0 g 20:: ': The cationic starch has a degree of substitution of 0.20; cationation is done in quatemers

:: with ammonium compound. The cationic starch and water are mixed in the reactor. PH of the solution

Is adjusted to 7 with acetic acid and 20% aqueous solution of both t-butyl hydroperoxide and '' 'sodium metabisulfite is added. Raise the temperature to 60 ° C and reactor: ...; A nitrogen atmosphere is provided for the duration of the reaction.

The supply of acrylic acid and acrylamide is started and lasts for 120 minutes. At the same time ; * start feeding, without addition, a solution of t-butyl hydroperoxide and sodium metabisulphite •, ϊ · for 150 minutes.

:: 30; ': Post-reaction after the feeds have been completed for 120 minutes with stirring at 60 ° C.

: '*: The reaction may be initiated by various initiators such as the oxidation-reduction reagent pair in the example above, e.g. a pair of copper sulfate-hydrogen peroxide, or 5 e.g. with a cerium salt. The catalyst may also be persulphate or another catalyst commonly used in emulsion polymerization.

Example 2 5 Testing of hand sheets

The paper used pulp - grit - wreck paper mill pulp and laboratory sheet mold. The sheets were made to a weight of 60 g / m2. The dosage of additives (cationic starch or product according to Example 1) is kg per tonne dry weight.

Test point 1 2 3 4 5 Wet tensile strength kNm / kg

Control 0 1.92

Cationic Starch 1 1.82

Cationic Starch 3 1.93

Example 1 Product 1 2.12

Example 1 Product 3 2.13 10 Wet tensile strength is determined from freshly wet (35% dry matter) sheets. The measuring device used pulls the paper strip at a constant speed (50 mm / min) and registers the paper; tensile strength required for breaking.

. :: The results show that the test product of the invention improves the wet tensile strength of the sheets, * ... · 15 which cationic starch alone does not.

Example 3 '*> ·' Laboratory sheets are made from pulp with 80% pulp and 20% pulp.

The dosage of additives is stated in kg / t. The sheets tested in the example are made with 20 fiber oriented sheet molds from which machine direction (MD) and transverse direction (cd) can be distinguished.

»· * *» 113968 6

Test point 1 2 3 4 Wet tensile strength Wet tensile strength MD kNm / kg CD kNm / kg

Catechol + glyoxal 1 + 1 2.06 1.35

Cationic Starch 3 2.26 1.35

Example 1 Product + 1 + 1 3.32 1.67 Glyoxal

Example 1 Product 3 3.21 1.46

Compared to cationic starch, it is clearly seen that the product of the invention improves wet strengths in both machine and transverse directions.

5

Example 4

Laboratory sheets are made from pulp containing 15% pulp, 20% scrap and 55% mechanical pulp and kaolin as a filler with a paper ash content of 20%. The dosage of additives is expressed in kg / t of dry matter. The sheets are made with a basis weight of 70 to 10 g / m2.

Normal pulp starch (MT) was also used in the formulation, which was dosed at 5 kg / t.

: Test point 1 2 3 4 Wet tensile strength Wet tensile strength IGT-pick MD kNm / kg CD kNm / kg m / s

Zero 0 2.1 1.2 2.27. Mass starch 5 2.4 1.2 2.66, ~ MT 5 + Ϊ 2 ^ 4 U 2 ^ 82 + eg 1 product .....: MT 5 + 2 2 ^ 9 U ~ 3 ~ 45, · · , + eg 1 product '!!.' When making these sheets, a fiber oriented mold was used. The wet tensile strength is improved

I I

'' 15 test products, mainly in the machine direction, at a dosage of 2 kg / t test product.

'·] These sheets also measured the IGT surface strength, and also showed a clear' 'healing to the 0 point and use of pulp starch alone.

Claims (6)

113968 IGT Picking describes how ink-printed paper withstands abrasion before the surface becomes fluffy and fibers become visible on the surface. 5 An additive for the production of paper and board comprising a polymerized product of at least one vinyl monomer in the presence of a cationic polysaccharide, characterized in that the cationic polysaccharide has a degree of substitution of from about 0.02 to about 0.50 and up to about 30% monomers by weight. dry weight of the working materials, wherein the monomer component comprises at least about 95% by weight of the amide. 2. Tillacetam enligt patent krav 1, kanknetecknad därav, att högst ungefar 5% enligt 5 molmängd av monomerkomponenten utgör vinylisk carboxylsyra. Additive according to claim 1, characterized in that up to about 5% of the monomer component of the monomer component is vinyl carboxylic acid. 15 3. Tillsatsämne enligt patent krav 1 eller 2, kännetecknad därav, att vid polymerisationen har använts monomerer högst ungefar 20% beräknat enligt utgängsämnenas torrvikt. 10 Additive according to Claim 1 or 2, characterized in that monomers are used in the polymerization up to about 20% based on the dry weight of the starting materials. 4. The tulipsacampus enligt face av patent crav 1-3, the tarsus davav, the att polysackari and the speckles stärkelse. An additive according to any one of claims 1 to 3, characterized in that the polysaccharide is • digested starch. 5. Användning av tillsatsämne enligt patentkrav 1 vid pappers- och cartonboardillverk- 15 Ning. Use of an additive according to claim 1 in the manufacture of paper and board. Use according to Claim 5, characterized in that the additive is applied in an amount of from 1 to 3 kg per tonne of dry matter. ; * Patent krav i '' 30 '* ·' 1. Tillsatsämne vid pappers- och kartongtillverkning, omfattande en produkmet polyme- 1: ': riserad av minst en vinylmonomer i nvarvaro av en cationic polysaccharides, :,,, tecknad därav , att substitutionsgrosen hos den cationic polysackariden and unge- Fär 0,02 - ungefär 0,50 och det vid polymerisationen har använts monomerer högst, 113968 ungefar 30% beräknat pä utgängsämnenas torrvikt, colors monomerkomponenten enligt molmängd omfatt. 6. Användning enligt patentkrav 5, kännetecknad därav, att per ton mass enligt torrsubstans doseras 1-3 kg tulle azam. I II II • * · »» »