JPH0357999B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an excellent water-soluble internal additive for papermaking that can be added to an aqueous dispersion of pulp in papermaking, particularly neutral papermaking, to improve filler retention, paper strength, and sizing. . Conventionally, in paper making, a rosin compound has been added to an aqueous pulp dispersion as a sizing agent, and sulfate has been used in combination with this. In recent years, anion-modified polyacrylamide has also been used in papermaking as a paper strength enhancer and filler retention improver. These internal additives are anionic and are used in acidic medium during paper making. However, these anionic internal additives do not have sufficient fixing properties to pulp fibers, and there is a problem of white water contamination.In addition, since they are used under acidic conditions, there are problems such as equipment corrosion.
In addition, the use of inexpensive calcium carbonate as a filler has been considered, but in this case, as mentioned above, there is a risk that calcium carbonate may be decomposed in an acidic medium, which poses a problem in its use. This led to the development of cationic internal additives for papermaking in which papermaking is carried out using neutral or alkaline media. In addition, examples of such cation-modified internal additives include cation-modified urea resin {Kentaro Toyoshima: Paper Paper Technology Association, Vol. 22, No. 2 (1967)}, melamine resin {Reinbold: Pulp and
Paper Magazine of Canada68, No.4, 110~
112 (1967)}, Cationic Starch {Engelhardt, G..
Zellstoff and Papier, 13, No. 9, 264-270.
(1967)} In addition, there are cationic polyamides {Nikkan Shigyo Tsushin No. 5551 (May 22, 1971)}, and other products with reactive sizing agents such as alkyl ketene dimers and alkenyl succinic anhydrides. Concomitant use is being considered. These cationic internal additives themselves have a positive charge and tend to bond with the negatively charged fiber pulp. Therefore, for example, cationic internal additives that are generally added during beating can easily bind to pulp, cause less turbidity in white water (turbid water), and reduce the pH of aqueous pulp dispersions.
Since it is neutral or alkaline, it has the advantage of being less likely to corrode paper-making equipment, but conventional products cannot be said to be sufficient in terms of increasing paper quality, improving sizing, or product cost. For this reason, polyvinyl alcohol (hereinafter referred to as polyvinyl alcohol) is used as a cationic internal additive.
Cationic modification of PVA (abbreviated as PVA) has attracted attention. Next, conventional cation-modified PVA is briefly described as follows. A. Method for post-modifying PVA (a) A method for producing cationic PVA containing a quaternary ammonium salt by reacting glycidyltrimethylammonium hydrochloride with PVA in the presence of an alkali catalyst, as disclosed in JP-A No. 52-3689. In addition, 3 with a glycidyl group opened in the same way
-Chloro-2-hydroxypropyltrimethylammonium hydrochloride has also been reported to be used in the reaction. (b) In the Journal of the Chemical Society of Japan 1975 (11) P1995-2000, PVA was reacted with epichlorohydrin,
Furthermore, it has been reported that cationically modified PVA can be synthesized by reacting polyethylene polyamine. (c) In Special Publication No. 30-5563 and Special Publication No. 31-3319, and in Polymer Papers 34 . 843 (1977), the introduction of amino groups by aminoacetalization of PVA was reported. B After copolymerizing vinyl acetate and a cationic monomer, the copolymer is saponified to become cationic.
How to obtain PVA (a) Polymer chemistry 8 . 467 (1951) discloses an example of saponifying a copolymer of vinyl acetate and vinylpyridine to obtain cationized PVA. (b) In JP-A-56-14504, aminoalkyl acrylamide is used as a cationic monomer, for example, CH ₂ =CHCONHCH ₂ CH ₂ CH ₂ N(CH ₃ ) ₂ A method for producing cationized PVA by saponifying a copolymer of PVA and vinyl acetate is disclosed. (c) According to the gist of the claims in JP-A-56-88413,

[expression] or

[Formula] n = integer of 2 to 6, X = inorganic negative group, R ₁ ,
R ₂ and R ₃ are lower alkyl groups, R ₄ is a hydrogen atom or lower alkyl group Cationization with the above structure
It is disclosed that PVA is a paper strength enhancer containing PVA as a main component. (d) According to the gist of the claims in JP-A-56-118997, In the above formula, R ₁ is alkylene or hydroxyalkylene group R ₂ and R ₅ are hydrogen or alkyl groups R ₃ and R ₄ are alkyl groups a),
A paper manufacturing method is disclosed in which a PVA resin containing one or two selected from (b), (c), and (d) is added to a pulp dispersion. The above is cationically modified PVA using the conventional method.
The following is a proposal regarding the following. In method A [(a), (b) and (c) of A above], PVA
However, this is known to be quite difficult. In addition, in method B [(a), (b), (c), and (d) of B above], a cationic monomer and vinyl acetate are first copolymerized, and then this is saponified to form a cationic PVA. I am getting
In general, copolymerizability is poor and it is a two-stage method requiring a saponification step, so it is expected to be difficult in actual production. Therefore, even if the cationized PVA obtained by these methods has improved effectiveness as a sizing agent for papermaking, it is considered to be problematic from an industrial perspective. Furthermore, in the description of the detailed description of the invention in the specification of JP-A-56-88413, from line 17 on the lower right of page 83 to line 5 on page 84, PVA is mentioned among the prior art. In the method of introducing cationic groups by post-modification, for example, it is difficult to produce a product with a constant degree of modification (degree of cationization). It often involves a crosslinking reaction, and the polymer tends to become insolubilized. Manufacturing costs are generally high. Difficulties in industrial manufacturing have been pointed out. Furthermore, it should be noted that in the detailed explanation column of the specification of the same issue, from page 84, top left column, line 11 to the same page, right column, line 5, aminoalkyl methacrylate is used as a cationic monomer. It is known that cationic copolymers are produced industrially and copolymerized with various monomers to obtain cationic copolymers. In this case, it is copolymerized with vinyl acetate as a copolymerizable monomer, but when this copolymer is saponified, the ester bonds of aminoalkyl methacrylate are simultaneously saponified, and the resulting modified PVA contains cationic groups. It has been pointed out that this may become impossible. However, despite the above reasons, we have been researching the grafting of PVA and found that the cationic monomers represented by the general formula () or (), which will be explained later, are used to graft PVA.
By graft copolymerizing with, it exhibits excellent effects as an internal additive for papermaking in terms of filler fixability, paper strength, sizing, etc., and has the advantage of being less likely to corrode papermaking equipment. We discovered that cationized PVA can be easily produced industrially,
The present invention has now been completed. That is, the present invention has the following gist (1). (1) Cationized polyvinyl alcohol obtained by graft copolymerizing a cationic monomer represented by the following general formula () or () in a proportion of 0.01 to 10 mol% with respect to the units constituting the polyvinyl alcohol. Mainly water-soluble internal additives for papermaking. general formula However, in the general formulas () and (), R represents a hydrogen atom or a methyl group, R ₁ represents an ethylene group or a 2-hydroxypropylene group, R ₂ represents a methyl group or an ethyl group, and X represents an inorganic anionic group. show. Moreover, the cationization according to the present invention
Unlike PVA, which is produced by copolymerizing a vinyl monomer and a cationic monomer and then saponifying this copolymer as described above, PVA is a cationic product obtained by graft copolymerizing a cationic monomer onto PVA.
Since it is PVA and there is no saponification step after graft copolymerization, one of the features of the present invention is that a predetermined amount of cationic groups can be introduced without the ester bond of the cationic monomer being decomposed during saponification. It is. Next, the production of cationic PVA based on the present invention will be explained. As a method for graft copolymerizing a cationic monomer represented by the above general formula () or () to PVA, (a) A PVA aqueous solution is added to the above general formula () or ().
A homogeneous graft copolymerization method in which a given amount of the cationic monomer shown is dissolved and polymerized using a water-soluble polymerization initiator (b) PVA is suspended in a mixed solvent of water and a non-solvent of PVA, There is a heterogeneous graft copolymerization method in which a water-soluble polymerization initiator and a cationic monomer represented by the general formula () or () are added and polymerized. The copolymer obtained by the graft copolymerization method (a) is preferable because it has excellent uniformity and high grafting efficiency. The graft copolymerization reaction solution obtained by this graft copolymerization can be used as it is as an internal additive in the papermaking process, but it can also be obtained in powder form through processes such as precipitation, filtration, and drying. Furthermore, although the graft copolymerization method (b) has less uniformity of grafting than the method (a), it is easier to take out the modified PVA as powder or granules. That is, there is an advantage that post-processing as a product is easy. In the above (a) and (b), in addition to the grafted cationized PVA, the general formula () or ()
Homopolymers of cationic monomers shown in are also mixed, but since these are naturally cationic polymers, even if they are mixed, the desired cationization can be achieved.
It does not inhibit the performance of PVA, and in some cases, a synergistic effect is expected. Next, there are no particular restrictions on the PVA used in the present invention, with an average degree of polymerization of 200 to 3000 and a degree of saponification of 60.
More than mol% of PVA can be used. Furthermore, water-soluble PVA in which acrylamide, ethylenically unsaturated carboxylic acid salts, olefins, α-olefins, fatty acid vinyl esters, alkyl vinyl ethers, etc. are copolymerized can also be used. As the cationic monomer used in the present invention, those represented by the general formula () or () are used, and for example, dimethylaminoethyl methacrylate and 3-trimethylammonium chloride-2-hydroxypropyl methacrylate are preferred. . The above general formula () is graft copolymerized to PVA
The amount of the cationic monomer represented by or () is 0.01 to 10 mol% based on the constituent units of the PVA.
and the cationization obtained at less than 0.01 mol%
The sufficient effect of PVA is not exhibited, and if the amount exceeds 10 mol%, the resulting PVA will gel and become difficult to dissolve in water. A particularly preferred range of the amount of the internal additive is 0.5 to 5 mol%. Further, a major feature of these grafted cationized PVs according to the present invention is that they are water-soluble. In addition, as the polymerization initiator used in the above graft copolymerization, persulfates such as potassium persulfate,
ammonium persulfate, or sodium persulfate;
Examples include hydrogen peroxide, cerium salts such as cerium ammonium nitrate, and redox systems using a combination of an initiator and a reducing agent are also used. Examples of reducing agents include sodium hyposulfite, acidic sodium sulfite, Rongarit, iron salts, and lithium halides. Next, the internal additive of the present invention is added to the aqueous dispersion during beating of paper pulp and fixed on the pulp fibers, or a filler is added at the same time, in the same way as general internal additives for papermaking. After that, the pulp fibers and the like are made into paper and dried by conventional methods to become paper. Furthermore, the internal additive of the present invention can be used in the form of an aqueous solution by spraying onto paper or by impregnation coating using a size press or the like. As mentioned above, the amount added internally in paper making varies depending on the type of paper pulp fiber and the purpose of the resulting paper, but is preferably 0.05 to 5.0% by weight based on the amount of dry pulp, preferably 0.1%.
~2.0% by weight is desirable. In this case, 0.05% by weight
If it is less than 5% by weight, the effects of fixing the filler and increasing paper strength will be weak, and if it exceeds 5% by weight, these effects will hardly be improved. Further, the internal additive according to the present invention is particularly effective for neutral paper making using calcium carbonate as a filler, but talc, titanium oxide, clay, etc. can also be used as a filler, and it can be used in combination with other paper sizing agents. It may also be used in combination with cationic polyacrylamide or cationic starch. As described above, cationized PVA according to the present invention
Its effectiveness as an internal additive for papermaking is that it is water-soluble, and unlike conventional cationic PVA, it is easy to manufacture, and it also has good fixing properties to pulp fibers even when added internally in neutral papermaking. At the same time, calcium carbonate as a filler is well fixed and the yield is improved. Therefore, the drainage property in paper making is good, and white water treatment becomes easier. The paper thus obtained has increased strength, for example burst strength, and improved sizing. Next, examples of the present invention will be shown. In the following, unless otherwise specified, "part" means "part by weight" and "%" means "% by weight", respectively. Example 1 PVA (average degree of polymerization 2400, degree of saponification 99.0 mol%)
After dissolving 100 parts in 900 parts of water, 20 parts of dimethylaminoethyl methacrylate was added, the atmosphere was replaced with nitrogen for 1 hour to remove dissolved oxygen, and then 0.6 parts of potassium persulfate was added and the temperature was raised to 45°C. Graft copolymerization was started, and after 3 hours, the temperature was further raised to 85°C, and the polymerization was completed after 1 hour. Then, the polymer solution was neutralized with hydrochloric acid, and the obtained polymer solution was dropped into 3 times the amount of methanol. Only the graft polymer was precipitated, filtered and dried. The resulting graft polymer was water-removed using a Soxhlet extractor with methanol, and the nitrogen content was measured by the Kieldahl method, and it was found to be 0.35% by weight, and the cation modification rate was
It was 1.13 mol%. Next, as a paper pulp raw material, pulp the cationized PVA of this example in 350 ml of Canadian Freeness 3% aqueous dispersion of L-BKP (converted to dry state).
0.2, 0.4, 0.6% each, and further L-
Dilute the BKP dispersion concentration to 0.3%, keep the pH as 7 to 8, and use the papermaking method of JISK8209 to produce a basis weight of 60±5.
g/m ² , press dehydrated at 3.5 Kg/m ² for 5 minutes, dry at 110° C. for 5 minutes, and condition the resulting paper at 20° C. and 65% RH for 48 hours. On the other hand, the white water during paper making was collected and concentrated, the concentration of cationized PVA in the white water was determined by the iodine coloring method, and the fixation rate of cationized PVA on the pulp was determined from this, and the fixation rate was 74, 74, It was 78.82%. Furthermore, JISK8113 is used for paper after humidity conditioning.
The breaking length was measured using a Tensilon tensile tester based on the above, and the specific rupture degree was measured using a Müllen bursting tester based on JISK8112. These results are shown in Table 1 below. Example 2 PVA (average degree of polymerization 1750, degree of saponification 99.5 mol%)
Dissolve 150 parts of lauryl alcohol-sulfate ester soda (Daiichi Kogyo Seiyaku Co., Ltd., Monogen Y-100) in 850 parts of water, and add 30 parts of dimethylaminoethyl methacrylate, 0.3 parts of potassium persulfate, and 0.06 parts of acidic sodium sulfite. was added to obtain cationized PVA in the same manner as in Example 1. In addition, the nitrogen content in the obtained cationized PVA was 0.61%,
The cation modification rate determined from this result was 2.01 mol%
It was hot. In this case, the cation modification rate of cationized PVA can also be determined by nuclear magnetic resonance spectroscopy. That is, the cationization in this example
According to the proton nuclear magnetic resonance spectrum of a heavy aqueous solution of PVA, the absorption at the shift position of 2.6 ppm is the H ₂ C=C of dimethylaminoethyl methacrylate unit.
( _CH2 ) _COOCH2CH2N ( _CH3 ) ₂ belongs to _CH2 of _-CH2 - _CH2- in the ethylene group moiety, _and this absorption intensity and vinyl alcohol unit

From the comparison value with the absorption intensity of shift 1.6 ppm attributed to CH ₂ in [Formula], the desired amount of grafting of the cationic monomer,
That is, the cation modification rate is 1.98 mol%,
Since it almost matches the 2.01 mol% determined from the nitrogen content by the Kieldahl method, either method can be used to measure the cation modification rate. Furthermore, Example 1 was prepared by using the cationized PVA of this example instead of the cationized PVA of Example 1.
Paper was obtained in the same manner as above, and the properties of the paper are also listed in Table 1. Example 3 PVA (average degree of polymerization 1750, degree of saponification 99.5 mol%)
Graft copolymerization was carried out under the same conditions as in Example 1, except that 150 parts of water, 850 parts of water, and 15 parts of 3-trimethylammonium chloride-2-hydroxypropyl methacrylate were used. The composition of the obtained polymer solution is cationized.
In addition to 15.25% PVA, it contained a homopolymer of 3-trimethylammonium chloride-2-hydroxypropyl methacrylate. The nitrogen content of the isolated cationized PVA is 0.18%,
Therefore, the cation modification rate was 0.59 mol%.
Note that paper was produced in the same manner as in Example 1 using the liquid obtained by the polymerization of this example as it was as an internal additive, and the properties of this paper are also listed in Table 1. Example 4 PVA (average degree of polymerization 1750, degree of saponification 99.5 mol%)
Pour 150 parts into 850 parts of water at 30°C, add 0.3 parts of potassium persulfate and 0.06 parts of acidic sodium sulfite while the PVA remains undissolved, continue stirring, and after 5 hours add 30 parts of dimethylaminoethyl methacrylate. plus 30
After graft copolymerization was carried out at °C for 5 hours, the mixture was neutralized with hydrochloric acid, immediately filtered, and dried. The cationized PVA obtained in this case is Example 1
Unlike the cationic modification of cationized PVA,
Although it is presumed to be heterogeneous because some solid-phase reactions are also carried out, it has the advantage that separation of cationized PVA is extremely simple. The nitrogen content of the obtained cationized PVA is 0.30
%, thus the modification rate was 1.0 mol%. Similar tests were conducted on paper obtained by making paper using the cationized PVA of this example under the same conditions as in Example 1, and the obtained properties are also listed in Table 1. Comparative Example 1 In place of the cationized PVA of Example 1, PVA
The paper obtained by making paper in the same manner as in Example 1 using {average degree of polymerization 2400, degree of saponification 99.0 mol% (K-24 manufactured by Denki Kagaku Kogyo Co., Ltd.)} was obtained by the same test method. The characteristic values obtained are also listed in Table 1 for comparison. Example 5 Using the cationized PVA of Example 2, calcium carbonate (manufactured by Nitto Funka Kogyo Co., Ltd.) was added to a 0.3% aqueous dispersion of L-BKP in 320 ml of Canadian Freeness.
NITOREX-70) is added at 30% to the pulp amount,
While stirring, add 0.2, 0.4, and 0.6% of the above cationized PVA to the pulp amount, below JISK8209
Paper was made to have a basis weight of 60±5g/ ^m2 based on ^the papermaking method of
It was dried at ℃ for 5 minutes. The paper thus obtained is 65
Humidity was controlled at %RH for 48 hours. The ratio between the amount of calcium carbonate contained in this paper and the total amount of added calcium carbonate was determined, and the yield rate was calculated from this ratio. In addition, the tearing length was measured using a Tensilon tensile tester based on JISK8113, and the specific rupture degree was measured using a Miuren bursting tester based on JISK8112. The results of each
Shown in the table. Comparative Example 2 Cationization of Example 2 used in Example 5
PVA instead of PVA {average degree of polymerization 1750, degree of saponification
99.5 mol% (K-17 manufactured by Denki Kagaku Kogyo Co., Ltd.)
A paper was obtained using the paper making method under the same conditions as in Example 5. The characteristic values of this paper are also listed in Table 2 for comparison. Example 6 A graft polymer was obtained in the same manner as in Example 2, using PVA with an average degree of polymerization of 550 and a degree of saponification of 88.4 mol % in place of the PVA used in Example 2. The cationized PVA thus obtained had a nitrogen content of 11.1%, and therefore a cationic modification rate of 3.80 mol%. Next, Canadian Freeness 320ml L-BKP
Calcium carbonate (NITOREX-70 manufactured by Nitto Funka Kogyo Co., Ltd.) was added to a 0.3% aqueous dispersion of 30% of the pulp, and then alkyl ketene dimer (Sizepine K-900 manufactured by Arakawa Chemical) was added as a sizing agent to the pulp. 0.4% was added, and 0.2, 0.4, and 0.6% each of the cationized PVA of this example was added to the pulp, and paper was prepared using the same papermaking method as in Example 5. The calcium carbonate yield, tearing length, and specific bursting strength of these papers were measured, and the degree of sizing was also measured based on TAPPI's standard test method, and these measured values are also listed in Table 3. . Comparative Example 3 In Example 6, PVA (average degree of polymerization 550, degree of saponification 88.4 mol%) was used instead of the same cationized PVA.
A paper was prepared using the same paper making method as in Example 6. The physical property values of this paper are also listed in Table 3 for comparison.

【table】

【table】

【table】

[Table] Table 1 shows that when the cationized PVA of the present invention is used as an internal additive in paper making, it has an extremely high fixation rate on pulp and has the effect of improving the strength of the resulting paper. It shows.
In addition, from this table, cationized PVA grafted in a heterogeneous system as in Example 4 is also found in Examples 1, 2,
It is interesting that the uniform system of No. 3 shows almost the same effect as the grafted cationized PVA, and has industrial significance. Next, Table 2 shows the cationized PVA of Example 2.
We compared the state of fixation of the filler calcium carbonate to the pulp in paper making using both PVA and non-cationized PVA, and the results showed that the amount of filler fixation was much greater with cationized PVA. Table 3 shows cationized PVA obtained by graft copolymerization using PVM with different bases, such as PVM with a degree of polymerization of 550 and a degree of saponification of 88.4 mol%.
It has also been shown to have effects such as improving size. As mentioned above, the cationized PVA according to the present invention has good binding to pulp during beating during paper making, and has a high retention rate of fillers, especially calcium carbonate.
Therefore, the freeness during filtration is good, the treatment of white water is easy, and the obtained paper quality is strengthened and the size is improved, and furthermore, compared to the production of cationized PVA by the conventional method. It's simple. Furthermore, the cationized PVA according to the present invention can be used as a surface sizing agent, an antistatic agent,
It is expected that it will be applied to polymer flocculants, emulsifiers for emulsions, household glues, etc.

Claims (1)

[Claims] 1. Cationization obtained by graft copolymerizing polyvinyl alcohol with a cationic monomer represented by the following general formula () or () in a proportion of 0.01 to 10 mol% based on the units constituting it. A water-soluble internal additive for papermaking mainly made of polyvinyl alcohol. However, in the general formulas () and (), R represents a hydrogen atom or a methyl group, R ₁ represents an ethylene group or a 2-hydroxypropylene group, R ₂ represents a methyl group or an ethyl group, and X represents an inorganic anionic group. show.