JPH03260193A - Water-resistant paper by chemical modification - Google Patents

Abstract

PURPOSE:To obtain reutilizable water-resistant paper capable of providing a high paper strength even in a wet state and reducing wet strength by treatment with NaClO in recovering by using N-halogenated pulp fiber. CONSTITUTION:The objective water-resistant paper obtained by carbamoylethylating pulp fiber, then reacting a hypohalite therewith, carrying out N-halogenation and forming sheets of paper from the resultant N- halogenated pulp fiber.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to waterproof paper that can obtain high paper strength even in a wet state by chemically modifying pulp fibers having hydroxyl groups.

[Conventional technology]

Traditionally, common methods for producing wet and dry paper strength sheets include adding a paper strength enhancer to pulp slurry to make paper, adding a sheet crosslinking agent, and mixing paper by combining with synthetic pulp. Can be mentioned. Paper strength agents used to impart water resistance are reactive ones such as melamine resin and shrimp chlorohydrin resin, and non-reactive ones such as aminated polyacrylamide (A-PAM) and polyethyleneimine (PEI). It is broadly classified into gender. Melamine resin improves paper strength by utilizing the reactivity of methylol groups generated by coexisting formaldehyde, and has been studied for a long time, but there are problems with the toxicity of free formalin and product stability (■ Michinori Tsuchiya, Paper and Pulp Technology Times. 24.7-14 (1981)). Polyamide polyamine shrimp chlorohydrin resin (PAE), which is currently widely used as a wet paper strength agent, is synthesized by reacting shrimp chlorohydrin with a condensation polymer of adipic acid and diethylenetriamine. It is added during paper making in hopes of covalent reactivity between chain epoxy groups and cellulose fibers, but its wet strength is far below the untreated dry strength (■, ■N, A, B
ates: Tappi, , 52.1
162-1168 (1969)). In addition, since A-PAM with a high amination rate is effective as a wet paper strength enhancer, it is thought that the amino group contributes to the increase in wet strength (Kyoji Suzuki, Hiroo Naka: Wood Science Society Journal. 2+1, 204-208 (1977)). PEI also shows an increase in wet paper strength. However, these wet-end additives have their own limits on the amount added in terms of fixing properties, papermaking properties, paper quality (formation), price, etc., and all paper strength enhancers are wet-end additives under normal papermaking conditions and within the range of addition amounts. It is difficult for the tensile strength to exceed 50% of the dry tensile strength without additives. As for the method of adding a crosslinking agent, there is a method of spraying a bisacrylamide compound or a diisocyanate compound onto the paper surface. During Japan and China, dimethylene ether bisacrylamide (ME
BA) was added in an amount of 3% based on the weight of BKP, and the wet tensile strength was 12 times that of untreated paper, and the dry tensile strength was 7% higher (Hiroo Naka, Mitsuhiro Morita, Ryo Senju - Paperback). Technical Association Journal, 25, 575-581 (1971,')). However, in this case as well, the ratio of wet paper strength to untreated dry paper strength (
The wet strength rate) remained at 41%. Furthermore, MEBA requires the addition of an alkali as a reaction catalyst during sheet production, and requires a heating temperature of 130° C. or higher during drying. On the other hand, diisocyanate type crosslinking agents also improve wet strength due to interfiber crosslinking, but they are difficult to add in aqueous systems, and the use of organic solvents poses practical problems. Although it is possible to impart water resistance by combining synthetic pulp and natural pulp, the original properties of paper are impaired, and the water absorbency and feel are inferior to ordinary paper. On the other hand, as an example of using N-chlorinated compounds to make paper water resistant, there is a report by Senju et al. who used an N-chlorinated derivative of carbamoylethylated starch as a paper strength enhancer (■Ryo Senju-・Sakio Higuchi, Kenji Takeshita, and Koichi Nakayama: Paperback Technical Association Journal, 27, 335-340 (1973)). According to reports, N-chlorinated starch shows excellent effects on lignin-containing pulp,
By using it in combination with a polymer containing amino groups, a remarkable effect of increasing paper strength has been obtained. By adding 1% of N-chlorinated starch with a degree of substitution of 10.7 to LUKP based on the pulp, the dry tensile strength increases by 52% and the wet strength increases approximately 11 times. (if substitution degree
(degree of 5substitution%
Represented by DS. ) is a constituent sugar residue (in this case glucose)
This is the average number of substituted hydroxyl groups per hydroxyl group. ) Therefore, the degree of substitution of 0.7 means that 0.7 hydroxyl groups per glucose residue in starch are replaced with N-CI-formed CB groups. ) However, the wet strength rate remains at 26%. With LBKP, the dry strength improvement rate was 28% and the wet strength improvement rate was 13% at the same addition rate.
It is only %. Overseas, Sm1th et al. quickly added a product obtained by treating carbamoylethylated starch with sodium hypochlorite under acidic conditions to LUKP and obtained a significant improvement in wet and dry paper strength, but they added a large amount of 10% to the pulp. However, the wet strength rate is about 60% (■H, E, Smjth et
al,: T a p p i , 5
3.1704-170g (1970)). In addition, as examples of fiber modification using carbamoylethylation, (1) carbamoylethylated cellulose fibers are graft-polymerized with acrylic esters to impart high elastic recovery properties (Japanese Patent Application Laid-Open No. 50-135395 Publication), (2) Production of cationic pulp by Hofmann decomposition of carbamoylethylated pulp (Sakio Higuchi, Ko Noma, Ryo Senju, Nishiba Technical Association Journal, 25, 187
-195 (1971); ■Special Publication No. 49-38708). Here, (1) is imparting high elasticity to the fibers,
(2) is intended to impart a positive zeta potential to the pulp fibers so that negative colloids can be adsorbed, and neither of them is intended to make the pulp fibers water resistant. Therefore, it is not sufficient to improve wet and dry strength.

[Problem to be solved by the invention]

However, although the above methods of adding various chemicals improve dry strength, wet strength cannot be said to be improved sufficiently.
Due to the addition of chemicals, there are problems such as toxicity due to free formalin, poor product stability, fixation of fillers, etc., paper-making properties, and formation, and problems with formation, water absorption, and texture due to the combination of synthetic fibers. The object of the present invention is to solve these problems and to obtain waterproof paper that has high paper strength even in a wet state.

[Means to solve the problem]

The present invention is obtained by carbamoylethylating pulp fibers, then N-halogenating them by acting with a hypohalite, and making paper using the N-halogenated pulp fibers.
Waterproof paper made by chemically modifying pulp fibers with hydroxyl groups. Pulp fibers that can be used in the present invention are not particularly limited as long as they have hydroxyl groups, and examples include chemical pulps such as hardwood and softwood, GP, P
GW, RMP, TMP. Examples include bleached mechanical pulps such as CTMP and CMPXCGP, unbleached pulps, and waste paper pulps such as DIP, and these pulp fibers can be used alone or in combination. The freeness of the pulp fibers is not particularly limited, and excellent improvement in paper strength can be obtained at any freeness. Therefore, pulp that has been beaten to a desired freeness may be used as the raw material pulp. Methods for carbamoylethylating pulp fibers include: Method 1: Michael addition of acrylamide to pulp fibers. F-OH+CH2-CHCONH2 →F -0-CH2CH2CON H2 Second method: After Michael addition of acrylonitrile to pulp fibers and cyanoethylation, hydrogen peroxide is applied to obtain a carbamoylated product. F-OH+CH2-CH-CN →F OCH2CH2CN F 0-CH2CH2CN +2H202→F O
CH2CH2CONH2+H20+02 (F represents fiber) A halogen compound is used to convert carbamoylethylated pulp fibers into N-halogenated pulp fibers. Examples of these halogen compounds include hypohalous acids such as sodium hypochlorite, potassium hypochlorite, calcium hypochlorite, sodium hypobromite, potassium hypobromite, and calcium hypobromite. These include compounds produced by blowing chlorine or bromine into aqueous solutions of alkali metal salts or alkaline earth metal salts, caustic soda, caustic potash, calcium hydroxide, magnesium hydroxide, and the like. As an example of obtaining N-halogenated pulp fibers, carbamoylethylated pulp fibers can be N-halogenated by reacting sodium hypochlorite in an alkaline environment. F 0−CH2CH2CONH2+NaQC1→F
OCH2CH2CON -CIN-halogenated pulp fibers can be used alone or in combination with non-N-halogenated pulp fibers. However, as the amount of non-N-halogenated pulp fibers increases, the wet and dry tensile strength improvement rate decreases in proportion. The range of CB degree is 0°01 to 0 in terms of degree of substitution (DS).
．． 06 is good, and if the degree of substitution is less than 0.005, high water resistance cannot be obtained. When the degree of substitution is 0.1 or more, the tear resistance is greatly reduced. The degree of substitution tf is the number of substituted CB groups per glucose residue in the cellulose fibers constituting the pulp. N-halogenated pulp fibers are made into a sheet using a paper machine, then dehydrated using a press and dried by heating. The papermaking temperature is preferably room temperature or lower from the viewpoint of stability of N-halogen, but if the papermaking time is short, a particularly low temperature is not required. Other additives that can be added when making the waterproof paper of the present invention include substances used in general paper making, such as light calcium carbonate, heavy calcium carbonate, talc, clay kaolin, etc. Various additives such as a filler, a sizing agent, a fixing agent, a retention agent, a cationizing agent, and a paper strength enhancer can be appropriately included, and the paper can be made in acidic, neutral, or alkaline conditions.

【Example】

The present invention will be explained in more detail based on examples, but is not limited thereto. The strength test in the examples was measured by the following method. Dry breaking length: JIS P811B Wet breaking length: JIS P8135 (30 minute immersion) Specific rupture degree: JIS P8112 (Mullen low pressure test) Folding strength: JIS P8115 Whiteness: JIS P8123 (Hunter whiteness) Example 1, Comparative Examples 1 to 3 LBKP beaten to freeness (csf) 426 ml
(absolute dry equivalent weight 50g), sodium hydroxide 2
g1 Add 8 g of acrylonitrile and pure water to bring the total amount to 500 g.
1, treated at 50°C for 3 hours to cyanoethylate (CE), and after washing the CE pulp with water, the CE pulp was treated with 50 g of hydrogen peroxide and 2 g of sodium hydroxide.
01 aqueous solution and treated at room temperature for 50 minutes to form carbamoylethylation (CB conversion).The degree of CB conversion is the degree of substitution.
(DS) was 0.04. This CB pulp (
After N-chlorination by adding 0.1 mol sodium hypochlorite alkaline solution 201 to 5 g (absolute dry equivalent weight), the paper was hand-sheeted, dehydrated with a press, and dried by heating to produce waterproof paper. For comparison, untreated pulp, CE-modified pulp, and CB-modified pulp were hand-made in the same manner to obtain sheets. Table 1 shows the strength test results for each treated pulp. As is clear from Table 1, the waterproof paper made from N-chlorinated pulp fibers exhibits superior strength in both dry and wet tensile strength, bursting, and folding resistance compared to untreated paper, CE paper, and CB paper. I understand that. Table 1 Pulp: LBKP Freeness (csr) 426 m
Degree of substitution**, number of substituents per glucose residue in cellulose constituting pulp Example 2, Comparative Examples 4 to 6 Freeness (cs') LUKP beaten to 440 ml
(absolute dry equivalent weight 50g), sodium hydroxide 1
．． Add 5g of acrylonitrile, 7g of acrylonitrile, and pure water to bring the total amount to 4.
001 and treated at 50°C for 3 hours to undergo cyanoethylation (C
After washing the CE-modified pulp with water, the CE-modified pulp was poured into a 5001 aqueous solution containing 5 g of hydrogen peroxide, 2 g of sodium hydroxide, and a trace amount of potassium iodide,
Carbamoylethylation (CB conversion) by processing at room temperature for 50 minutes
The CB group content of 11 g'' was 1.5%. After N-chlorination by adding 0.1 mol sodium hypochlorite alkaline solution 201 to this CB-formed pulp (bone dry equivalent weight 5 g), A water-resistant paper was prepared by hand-sheeting, dehydration using a press, and heating and drying. For comparison, untreated, CE-modified and CB-modified pulps were hand-papered in the same manner to obtain sheets. CB group content: LUKP contains lignin and DS
Since it is not appropriate to express it in terms of CB group content (%). CB group content CB group content (%) - X100 CB-formed pulp absolute dry weight The strength test results of each treated pulp are shown in Table 2. Similar to bleached kraft pulp (L B K P) in Table 1,
It is shown that excellent water resistance can be obtained even with unbleached KP (Table 2). Dry tensile strength, bursting strength, and folding strength are greatly improved, and whiteness is also slightly improved. It is thought that the lignin content does not have a particularly large negative effect on the development of water resistance. Table 2 Pulp: LUKP Freeness (Cs') 440 m
Examples 3 to 7, Comparative Example 7 Freeness (csr) 420 mH: Beaten LBKP
(absolute dry equivalent weight 48 g), the degree of CB conversion is 11 (D
S) is 0.008.0.019.0.03.0.0
Carbamoylethylation (CB
) and these CB-formed pulp fibers (absolute dry equivalent weight 5g)
) with 0.1 molar sodium hypochlorite alkaline solution 20
After adding 1 to N-chloride, the paper was hand-papered, dehydrated using a press, and dried by heating to produce waterproof paper. Table 3 shows the strength test results for each pulp. Table 3 shows that the wet and dry tensile strength, bursting degree and folding strength improve as the degree of substitution increases, and in particular, the wet tensile strength becomes stronger than the dry tensile strength of untreated paper when the DS exceeds 0.05. It should also be noted that even at a very low degree of substitution such as DS0°008, the dry tear length is about 1-54 times that of untreated paper and the wet tear length is about 20 times that of untreated paper. Table 3 Pulp: LBKP Freeness (csf) 420 m
l Example 2 N-chlorinated pulp Comparative example: Untreated pulp Examples 8 to 10, Comparative Examples 8 to 10 The freeness of LBKP (cs
Handmade waterproof paper was obtained in the same manner as in Example 1, except that f) was beaten and the degree of CB substitution was changed to 0.03 (DS). As a comparative example. Untreated pulp fibers were beaten in the same way, hand-papered, dehydrated with a press, and heated to dry to create a sheet. The strength test results of each beaten pulp are shown in Table 4. As shown in Table 4. , the pulp with a freeness of 638 m1 is unbeaten pulp, but it has been treated with N-chlorination (DS0.0
3) By doing so, the dry tearing length becomes as strong as a normal beaten sheet, and the wet tearing length exceeds 2 km. Pulp with high freeness (csr) has a high dry strength improvement rate. This is because the strength of untreated paper itself is lower than that of high-filtration wood bark. In the case of pulp having a degree of CB of DS 0.03 at any freeness, it is thought that an improvement in dry tearing length of about 2.5 to 3 km can be obtained. Table 4 Example 2 N-Chlorinated Pulp (LBKP) Comparative Example 2 Untreated Pulp Examples 11 to 14, Comparative Example 11 Freeness (csf) 455
The degree of CB conversion of LBKP beaten to ml is the degree of substitution” (DS)
The CB-treated pulp fibers were N-chlorinated, and the blending ratio of the N-chlorinated pulp fibers and the reduced-volume untreated pulp fibers was 0:1.3:1. 1:
1.1:3.1:0, hand-papered, dehydrated with a press, and heated to dry to produce waterproof paper. Table 5 shows the strength test results for each mixed pulp. As can be seen from Table 5, the wet tensile strength varies depending on the formulation.
Although a decrease of more than that percentage is observed, each strength generally shows a strength value that is almost commensurate with the blending ratio. Table 5 A: N-chlorinated pulp (LBKP substitution degree "0.0"
4) B: Waterproof paper was prepared by dehydration using an untreated pulp press and drying by heating. For comparison, untreated TMP pulp was similarly hand-milled to obtain a sheet. Table 6 shows the strength test results for each pulp. As is clear from Table 6, it is possible to impart a high degree of water resistance even to lignin-rich mechanical pulp such as unbleached TMP by N-chlorinating it. The reason why the improvement rate for each strength is higher than that of untreated paper (152% increase in dry tearing length) is because the strength of untreated paper itself is low, similar to the case of LBKP's unbeaten pulp. . Example 15, Comparative Example 12 CB-modified TMP with a CB group content of 0.62% was prepared from unbleached TMP beaten to a freeness (csf) of 3791 in the same manner as in Example 2, and further treated with hypochlorite. N-chlorinated TMP (substituent content 0.91
%), then hand-papered and pulped Table 6 Pulp: TMP Freeness (cs') 379a+1
Example 16, Comparative Example 13 Freeness (csf) LBKP beaten to 430 ml
(absolute dry equivalent weight 48 g), the degree of CB conversion is 11 (D
Carbamoylethylation (
CB) and these CB-converted pulp fibers (absolute dry equivalent type J
i5 g) was N-chlorinated by adding θ, 1 mol sodium hypochlorite alkaline solution 201, hand-sheeted, dehydrated with a press, and dried by heating at 105°C for 10 minutes. After that, the sheets were dried at room temperature (20° C.) for 24 hours and the strengths of the prepared sheets were compared. The strength values when the untreated pulp was made into a sheet by the same drying process are also shown. The results are shown in Table 7. As can be seen from Table 7, 1
When heated and dried at 05°C, the dry tearing length is improved by about 44% compared to the untreated sheet, but even when dried at room temperature, the dry tear length is about 39% higher than that of the untreated sheet.
%improves. Even in wet tearing length, paper treated at room temperature retains more than 90% of that of paper treated with heat and drying. Therefore, it can be seen that in the case of N-chlorinated waterproof paper, good water resistance can be obtained even without high-temperature heat treatment. As can be seen from Table 8, both LBKP and NBKP are N.
-Dry and wet tensile strength is improved by chlorination. Pulp: LBKP freeness (csf) 430 it
Examples 17-21, Comparative Examples 14-15 In the same manner as in Example 1, the samples were beaten to a freeness (csf) of 426 ml.
B K P and freeness (csf) 455 s+l The degree of CB conversion of the beaten NBKP was adjusted to the degree of substitution ゚'' (DS) to be 0.05. The resulting N-chlorinated pulp fibers, untreated LBKP, and NBKP were hand-milled, dehydrated using a press, and heated to dry using the formulations shown in Table 8 to produce waterproof paper.Strength of each mixed pulp The test results are shown in Table 8. Degree of substitution'''+0. 05 (N-chlorinated pulp)

【Effect of the invention】

The characteristics of the waterproof paper of the present invention are that, unlike water resistance made by adding chemicals, there is no risk of damaging the paper base by adding chemicals, and of course there is no need to consider yield, and high temperature treatment is required for drying after paper making. I don't. The resulting waterproof paper has good texture, and its feel and surface properties are almost the same as conventional paper. Since hydrogen peroxide is used during CB conversion, the whiteness is slightly improved compared to untreated paper. Can withstand repeated wet and dry conditions. In addition, upon recovery, the wet strength is reduced by NaCl0 treatment and reuse is possible.

Claims (1)

[Claims] (1) A chemically modified waterproof paper characterized by using N-halogenated pulp fibers.