JPS6363678B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a paper making method. Paper making by adding various acrylamide polymers to an aqueous slurry of pulp has been practiced for a long time. Various types of acrylamide polymers are known, including anionic, cationic and amphoteric ones. For example, anionic products include copolymers of acrylamide and vinyl monomers having carboxyl or sulfone groups, and partial hydrolysates of polyacrylamide; cationic products include primary to quaternary amino groups. Copolymers of vinyl monomers and acrylamide or polyacrylamide are introduced with amino groups by various modification methods such as Hofmann reaction or Mannitz reaction, and amphoteric ones are produced by introducing anionic groups into polyacrylamide using the same recipe. and cationic groups are known. Among these, amphoteric acrylamide polymers have the advantage of being usable over a wide range of pH from 4 to 9, and are beginning to be used as paper strength enhancers. The strength is still not always satisfactory. In addition, the above various polyacrylamide polymers may be used in combination with each other or with other polymers, i.e., anionic acrylamide polymers and polyamide polyamine epichlorohydrin resins may be used (Japanese Patent Publication No. 45-1973).
31690) and the combined use of anionic polyacrylamide with a Hofmann reaction product (Japanese Patent Application Laid-Open No.
(Refer to Publication No. 26501) have also been proposed, but the current situation is that even when these are used in combination, it is not possible to impart satisfactory paper strength to Shosei paper. Moreover, the above-mentioned proposed special public
In the case described in Publication No. 31690, the pH range for use is limited to the acidic side, which has the disadvantage of limiting the application.
Furthermore, the wet strength is high, which may be undesirable depending on the type of paper. The present invention provides a new method for making paper by selecting specific amphoteric polyacrylamide polymers from among the various polyacrylamide polymers mentioned above and using them in combination in a certain order. That is, the present invention adds 1 to 20 mol% of anionic groups and 1 to 30 mol% of cationic groups to an aqueous slurry of pulp.
Acrylamide polymer containing mol% (),
A method for making paper, which comprises adding an acrylamide polymer () containing 1 to 20 mol% of sulfate and anionic groups and 1 to 30 mol% of cationic groups in the above order, and then making paper. . According to the method of the present invention, based on the combination of the specific amphoteric acrylamide polymers () and () in the above order, an excellent It is possible to obtain paper having paper strength. The strength (specific compressive strength and specific bursting strength) of the paper obtained by the method of the present invention is particularly excellent, as shown in the Examples described later. In the present invention, it is essential to add an amphoteric acrylamide polymer (2), sulfuric acid, and an amphoteric acrylamide polymer (2) to a pulp slurry in this order before papermaking. The acrylamide polymer () used above contains 1 to 20 mol% of anionic groups, such as sulfone groups, carboxyl groups, etc., preferably 2 to 10 mol%.
Mol% and cationic groups such as primary amino groups, 2
Any water-soluble polymer may be used as long as it contains 1 to 30 mol%, preferably 2 to 15 mol%, of primary amino groups, tertiary amino groups, quaternary ammonium groups, etc., and has acrylamide as the main constituent monomer. The introduction of anionic groups into such polymers can be achieved by, for example, acrylic acid,
This can be carried out by copolymerizing a monomer having an anionic group such as methacrylic acid, vinyl sulfonic acid, or sulfonated styrene with acrylamide, or by hydrolysis or sulfomethylation of the amide group in the acrylamide polymer.
In addition, the introduction of a cationic group can be achieved by copolymerizing a monomer containing a cationic group with acrylamide, or by cationically modifying an anionic acrylamide polymer by Mannitz reaction, transamidation reaction, Hofmann reaction, etc. It is done by twisting. Regardless of the method used, the acrylamide polymer () used in the present invention must contain anionic groups and cationic groups in the above-mentioned specific ratios, and those that fall outside of this range are The intended effect of the present invention cannot be achieved. Specifically, the cationic group contained in the above polymer (2) is present in the polymer in the form of various amino groups or their acid addition salts as shown below. [In (1) to (6) above, R ⁰ represents a hydrogen atom or a methyl group, A represents an alkylene group having 2 to 4 carbon atoms, B represents an alkylene group having 1 to 4 carbon atoms, and R ¹ to R ⁸ each represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. ] Examples of the acid used to form each of the above forms of acid addition salts include inorganic acids such as hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid, and organic acids such as formic acid, acetic acid, propionic acid, and oxalic acid. Further, among the anionic groups contained in the above polymer (), the quaternary ammonium base can be obtained by known quaternization means. 4 used for the quaternization
Grading agents include, for example, alkyl halides or aralkyl halides such as ethylene bromide, butyl bromide, benzyl bromide, methyl chloride, ethyl chloride, benzyl chloride, and methyl iodide; dimethyl sulfate, diethyl sulfate, dimethyl sulfite, and phosphoric acid. Examples include inorganic acid esters such as dimethyl; and epihalohydrins such as epichlorohydrin and epibromohydrin. Of course, quaternization using these quaternizing agents may be carried out on the monomer or its acid addition salt prior to producing the copolymer in the present invention, or may be carried out on the monomer or its acid addition salt after producing the copolymer. It may also be applied to the amino groups contained therein. The above-mentioned acrylamide-based polymers into which various anionic groups and cationic groups are introduced are basically obtained using acrylamide as a constituent monomer, but as long as it is water-soluble, it can be copolymerized with this in addition to the above-mentioned acrylamide. may contain other monomer units. Examples of monomers constituting the monomer unit include vinyl esters such as vinyl acetate and vinyl propionate; styrene, α
- Vinyl aromatic hydrocarbons such as methylstyrene and vinyltoluene; α,β-unsaturated nitriles such as acrylonitrile and methacrylonitrile; methyl acrylate, methyl methacrylate, ethyl acrylate, butyl acrylate, butyl methacrylate,
Examples include alkyl esters of acrylic acid or methacrylic acid having 1 to 8 carbon atoms such as 2-ethylhexyl acrylate, and nonionic monomers such as methacrylamide, glycidyl methacrylate, N-methylolacrylamide, and diascent acrylamide. It can be used as a monomer unit other than the above. Among the above acrylamide polymers (), the preferred one is the viscosity of a 10% by weight aqueous solution (25
℃) is about 100~1000000cps, especially about
500 to 100,000 cps is suitable. Furthermore, the acrylamide polymer () used in the present invention contains 1 to 20 mol% of anionic groups.
Preferably 2 to 10 mol%, 1 to 30 cationic groups
It is an amphoteric copolymer containing preferably 2 to 15 mol% by mole, and in this respect belongs to the same category as the acrylamide polymer (2). That is, the acrylamide polymer () may be the same as or different from the acrylamide polymers () described above, and may be used in an appropriate combination. In the present invention, the amount of the acrylamide polymer () and the acrylamide polymer () added to the pulp depends on the type of each, the use of the paper, etc., and is usually based on dry weight, although it is not limited. about 0.05-3%, preferably about 0.1-2%
The total amount is preferably in the range of about 0.1 to 5%. The amount of sulfuric acid band used also depends on the type of pulp, the papermaking water, the type and amount of the two types of acrylamide polymers used, etc., so it is generally about 0.5 to 0.5 - based on the dry weight of the pulp, although it is not limited. 5
It may be expressed as a percentage. The method of the present invention is different from a normal paper making method, except that the acrylamide polymer (), sulfuric acid, and acrylamide polymer () are sequentially added to the aqueous pulp slurry in this order. isn't it. The aqueous pulp slurry to which the method of the present invention can be applied is not particularly limited. Any dispersion can be used. Further, in the paper making process, various additives commonly used in paper making, such as ordinary sizing agents and fillers, may be added to the pulp aqueous slurry as in the past. Further, the paper obtained according to the present invention includes not only ordinary western paper but also paperboard. Hereinafter, production examples of acrylamide polymers used in the present invention and for comparison will be given, and then Examples will be given. Production Example 1 Acrylamide was placed in a four-necked flask equipped with a stirrer, reflux condenser, thermometer, and gas inlet tube.
87.7g, acrylic acid 9.9g, 48% caustic soda 9.2g
and 557 g of deionized water were charged, and the mixture was heated to 45° C. while stirring while passing nitrogen gas. Then 0.18g of ammonium persulfate and 0.08g of anhydrous sodium bisulfite.
As soon as g is added, the polymerization reaction starts and the internal temperature reaches 90.
℃ reached. After keeping the temperature for 3 hours, the mixture was diluted with 3.33 g of deionized water to obtain an aqueous copolymer solution with a nonvolatile content of 10% by weight. The pH and viscosity of this aqueous solution (25
°C, Burckfield viscometer) are respectively
It was 6.5 and 4300cps. This copolymer consists of 90 mol% acrylamide and 10 mol% acrylic acid. Hereinafter, this will be referred to as paper strength agent A. After adjusting the monomer aqueous solution shown in Table 1 below to pH 4.5 with sulfuric acid or caustic soda, a copolymerization reaction was carried out in the same manner as above to obtain an acrylamide polymer (paper strength agent B to L) having properties as shown in Table 1 below. )
I got it. Table 1 also lists the above-mentioned paper strength agent A.

[Table] In Table 1, the anionic monomers and cationic monomers indicate the following compounds, respectively. <Anionic monomer> AA...acrylic acid MAA...methacrylic acid <cationic monomer> C-1...dimethylaminoethyl methacrylate C-2...diethylaminoethyl methacrylate C-3...trimethylmethacryloyloxyethylammonium chloride C-4...3-trimethylmethacryloyloxy-2-hydroxypropylammonium chloride C-5...N-(N',N'-dimethylaminopropyl)acrylamide C-6...N-(N',N'-dimethylaminopropyl)methacrylamide C-7...Trimethyl(3-acrylamidopropyl)ammonium chloride C-8...dimethylallylammonium chloride C-9...2-vinylpyridine Production example 2 Acrylamide 93.8g, 80% acrylic acid aqueous solution
6.3g, 48% caustic soda 4.6g and deionized water 560g
A polymerization reaction was carried out in the same manner as in the case of paper strength agent A using g, and the nonvolatile content was 10% by diluting with deionized water.
Copolymer with a viscosity of 10,000 cps (acrylic acid 5 mol%)
An aqueous solution was obtained. To 1000g of this aqueous solution, 1.3g of 48% caustic soda, 18.8g of 50% dimethylamine aqueous solution and
Add 11.4 g of 37% formalin and react at 45°C for 1 hour, then dilute with deionized water to give a non-volatile content of 10%.
An acrylamide polymer aqueous solution having a pH of 9.8 and a viscosity of 4400 cps was obtained. This is referred to as paper strength agent M. Production Example 3 In the same manner as in Production Example 2 above, except that 9.4 g of 50% dimethylamine aqueous solution and 5.7 g of 37% formalin were used, the nonvolatile content was reduced to 10 after dilution with deionized water.
%, pH 9.8, and viscosity 6300 cps. This is referred to as paper strength agent N. Production example 4 10% of polyacrylamide (average molecular weight 700,000)
Cool 200g of aqueous solution to 15℃, add 18.6g of 12% sodium hypochlorite aqueous solution, and 48% caustic potassium aqueous solution.
160 g of a mixed solution consisting of 4.6 g and water was added dropwise over 30 minutes, and the mixture was kept warm for an additional hour. During this time, the liquid temperature was maintained at 20°C. Then, the pH was adjusted to 4.5 with hydrochloric acid. Thus, 9.5 mol% of amino groups (-NH ₂ ), carboxyl groups
6 of amphoteric acrylamide polymer containing 3.2 mol%
% aqueous solution was obtained. This is referred to as paper strength agent O. Production example 5 Acrylamide 51.2g, acrylonitrile 25.5g
g and 425 g of deionized water were charged, and heated to 50° C. while stirring and passing nitrogen gas. Then ammonium persulfate 0.61g and acidic sodium sulfite 0.11g
was added and kept at 80°C for 3 hours. Further, 175g of deionized water was added and kept at 70℃, 5.8g of ethylenediamine and 3g of 48% caustic soda were added and kept at the same temperature for 1 hour, then 55g of deionized water and 62.5g of deionized water were added.
% sulfuric acid was added and cooled. Thus, a 13% aqueous solution of an amphoteric polymer containing 6.8 mol% of amino groups (-CONHCH ₂ CH ₂ NH ₂ ) and 8.0 mol% of carboxyl groups was obtained. This is referred to as paper strength agent P. Production example 6 Aqueous solution of commercially available polyamide polyamine epichlorohydrin resin (pH 4.5, non-volatile content 10%, viscosity
80cps). This is called paper strength agent Q. Examples 1 to 14 The paper strength agents obtained in each of the above production examples are shown in Table 2 below.
They are used as acrylamide polymers () and (), respectively, as shown in . These paper strength agents are used in an amount such that the total weight in terms of solid content is 0.5% of the pulp (on a dry weight basis, the same applies hereinafter). Table 2 below shows the types and combined use ratios (weight ratio).

【table】

[Table] First, paper strength agent () (aqueous solution of the above acrylamide polymer ()) was added to L-UKP 1% slurry with a freeness of 500mlcsf, and then sulfuric acid was added to the pulp (on a dry weight basis, the same applies hereinafter). 3% or 1.5
%, and further added a paper strength agent () (aqueous solution of the above acrylamide polymer ()), using a Tatsupi Standard Sheet Machine to weigh 160g/
Paper is made so that it becomes ^m2 . The pH during paper making was 4.5 when 3% sulfuric acid was used and 5.6 when 1.5% sulfuric acid was used. Next, press dehydrate for 5 minutes at 7Kg/ ^cm2 , dry for 4 minutes in a rotary dryer with a surface temperature of 120℃, and then
Obtain paper by controlling the humidity at 20℃ and 65% RH for more than 24 hours. The properties of the paper obtained above were tested by the following method. Bursting strength: According to JIS P 8131. Ring compressive strength...according to JIS P 8126. Water-based…according to JIS P 8121. The results are shown in Table 3 when using 3% sulfuric acid band.
Table 4 shows the cases where 1.5% sulfuric acid band is used.
In each table, as a control, cases in which neither of the above-mentioned paper strength agents () and () were used are also shown. Further, the Example No. corresponds to the combination example No. in Table 2 above.

【table】

【table】

[Table] Comparative Examples 1 to 11 The paper strength agents (acrylamide polymers) shown in Table 5 below were used alone at 0.5% based on the pulp, or in combination (total: 0.5% based on the pulp), and the above examples were used. Repeat the same operation to obtain finished paper.

[Table] Tables 6 and 7 show the results of performing the same tests as in the above example on the obtained paper. table-
Table 6 shows the case where 3% sulfuric acid was used, and Table 7 shows the case where 1.5% sulfuric acid was used. As a control, each table also shows the results obtained when neither of the above-mentioned paper strength agents () and () were used. Furthermore, the comparative example numbers in each table correspond to the example numbers in Table 5 above.

【table】

[Table] Comparison between Table-3 and Table-6 above and Table-4 and Table-
As is clear from the comparison with No. 7, it is clear that the method of the present invention yields paper having extremely excellent paper strength. Examples 15-28 Paper strength agents () and () were used in combination at the ratio shown in Table 2 above in an amount that was 0.5% of the total pulp (combination examples Nos. 1-14 were used as Examples 15-28, respectively). ) Obtain paper as follows. That is, first add paper strength agent () to L-BKP 1% slurry with a freeness of 450mlcsf, then add 2.5% or 1% of sulfuric acid based on the pulp, and then add paper strength agent ()
was added, and paper was made using a Tatsupi Standard Machine to a weight of 50 g/m ² . during paper making
pH is 4.6 when using sulfate band 2.5%, and 1%
It was 5.4 when I used it. Next, press dehydrated at 7Kg/ ^cm2 for 5 minutes, dry for 1 minute in a rotary dryer with a surface temperature of 100℃, and then
The paper was conditioned at 20° C. and 65% RH for 24 hours or more, and the properties of the resulting paper were tested using the following method. Internal strength: Internal bond tester Tappi RC
308, manufactured by Kumagai Riki Co., Ltd.). Rupture length: According to JIS P 8113. The results are shown in Table 8 when using 2.5% sulfuric acid band.
Table 9 shows the cases where 1% sulfuric acid band is used.
The above paper strength agents () and () are shown in each table as a control.
The results obtained when neither of these methods are used are also shown.

【table】

[Table] Comparative Examples 13 to 24 Each of the paper strength agents (Examples No. 1 to 12) shown in Table 5 above was added to the pulp at 0.5% (if used together, the total amount was
0.5%), and the same operations as in Examples 15 to 28 above were repeated to obtain paper. The obtained paper was subjected to the same tests as in Examples 15 to 28, and the results are shown in Tables 10 and 11 below. Table 10 shows the results when using 2.5% sulfuric acid, and Table 11 shows the results when using 1% sulfuric acid. Each table shows the results when no paper strength agent is used ( The results of control) are also shown. Further, Comparative Examples No. 13 to 24 in each table correspond to cases where paper strength agents 1 to 12 in Table 5 were used, respectively.

【table】

[Table] Comparison between Table 8 and Table 10 above and Table 9 and Table
As is clear from the comparison with No. 11, it is clear that according to the method of the present invention, a paper product exhibiting extremely excellent internal strength and tearing length can be obtained.

Claims (1)

[Claims] 1 Add 1 anionic group to the pulp aqueous slurry
Acrylamide-based polymer containing ~20 mol% and cationic group (), 1-20 mol% of sulfate and anionic group, and 1-30 mol% of cationic group A method for making paper, characterized in that the paper is made after adding the combination () in the above order.