JP7588370B2 - Papermaking Additives - Google Patents

Description

The present invention relates to an additive for use in the papermaking process prior to papermaking. Specifically, the present invention relates to a papermaking additive that efficiently removes colloidal substances that have adverse effects in the papermaking process, reduces the moisture content of the pulp sheet after drainage in the wire part, and further enhances the strength of the finished paper.

In paper manufacturing, anionic trash (anionic impurities), micro-pitch, and turbidity components in papermaking raw materials are increasing due to an increase in the recycled paper content, neutral papermaking, and closed papermaking water. As long as these anionic trash, micro-pitch, and turbidity components are present in the papermaking raw materials in a fine state, they rarely cause defects in papermaking, but they become agglomerated by stirring, aeration, pH change, and chemical addition, causing stains and defects in paper products. Pitch components that do not adhere to pulp fibers and become agglomerated become coarse sticky materials involving fine fibers and fillers, and not only do they adhere to papermaking equipment and tools such as fan pumps, inside pipes, wires, felts, and rolls, but these adhesions also peel off and get on wet paper, causing papermaking defects. Typically, the surfaces of anion trash and micro-pitch are anionically charged, so a commonly used method is to add cationic or amphoteric polymers known as pitch control agents before they grow and coarsen (become pitch) to neutralize the charge and treat the anion trash or micro-pitch or reduce its adhesion (Patent Documents 1 to 4).
In addition, in the manufacture of paper, particularly in the manufacture of paperboard such as liners and core raw paper, there is a strong demand for improved drainage in the wire part and improved drying in the dryer part from the viewpoint of improving production efficiency by increasing the papermaking speed in the papermaking process. Polyethyleneimine and polyacrylamide (PAM)-based drainage improvers are widely used, and these are often used in combination with cationic starch and aluminum sulfate. In addition, the combined use of PAM-based and colloidal silica (Patent Document 5) has also been proposed for the purpose of improving drainage.
Furthermore, anionic, cationic or amphoteric acrylamide polymers are widely used as paper strength enhancers that impart strength to paper. However, in recent years, due to an increase in the proportion of waste paper used in paper mills, raw pulp containing short fibers derived from waste paper and having weak paper strength has been used, making it difficult for the paper strength enhancers to exert their effects.
In order to maintain the paper strength effect in these papermaking environments, a method for increasing the molecular weight of a paper strength agent (Patent Document 6) and a paper strength agent containing a copolymer whose weight average molecular weight and molecular weight distribution are controlled within a specific range (Patent Document 7) have been disclosed.
These papermaking additives are all related to treating anionic trash or micropitch, improving drainage and drying properties, and increasing paper strength, respectively, but no polymer composition that combines all of these effects is known.
Patent Documents 8 and 9 disclose a method for improving retention and drainage by adding a hydrophobic copolymer to a papermaking slurry. Only anionic hydrophobic copolymers have been specifically synthesized, and no cationic hydrophobic copolymers have been synthesized, and therefore their effects have not been confirmed. In addition, the effects of different ionic properties cannot be predicted, and no synthesis method or function of cationic hydrophobic copolymers is disclosed. Furthermore, the drying properties of the pulp sheet after dewatering and the strength of the paper are not addressed as technical objectives.

JP 2002-173893 A JP 2002-212897 A JP 2003-221798 A JP 2011-026746 A Japanese Patent Application Publication No. 9-279498 Japanese Patent Application Publication No. 2-61197 JP 2018-12909 A Special Publication No. 2003-517104 Special Publication No. 2008-545892

The objective of the present invention is to provide a papermaking additive that has the effect of removing pitch components that cause deterioration in quality and paper breaks due to stains and defects in paper during the papermaking process, the effect of reducing the moisture content of the pulp sheet after dehydration to increase papermaking efficiency, and the effect of increasing paper strength.

The present inventors have discovered that a polymer obtained by polymerizing monomers having as main monomers a specific composition ratio of a cationic monomer and a hydrophobic monomer has excellent properties for removing turbidity from pitch components and the like, reduces the moisture content of a dehydrated pulp sheet, and further has the effect of increasing the strength of the paper produced, thereby arriving at the present invention.
The papermaking additive of the present invention is a polymer obtained by polymerizing a monomer mixture containing a cationic monomer and a hydrophobic monomer as essential components, the monomer mixture containing 70 to 99% by mass of the cationic monomer and 1 to 30% by mass of the hydrophobic monomer.

By using the polymeric papermaking additive of the present invention in the papermaking process, substances that cause stains and defects in paper products, such as anion trash, micro-pitch, and turbidity components, can be efficiently removed, improving the drainage and drying properties of the pulp sheet in the papermaking process, improving production efficiency by increasing the papermaking speed, and further improving the strength of the finished paper.

The present invention will be described in detail below.
Polymerization of the polymer in the present invention can be carried out by known methods such as aqueous solution polymerization, suspension polymerization, dispersion polymerization in salt water, etc., but aqueous solution polymerization is preferred. For example, a monomer mixture, water, a surfactant, and a radical polymerization initiator are added to a predetermined reaction vessel, and the mixture is stirred and heated in an inert gas atmosphere such as nitrogen gas to obtain the target polymer.

Examples of cationic monomers include salts of inorganic or organic acids such as dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, dimethylaminopropyl (meth)acrylamide, and diethylaminopropyl (meth)acrylamide, or monomers having quaternary ammonium salts obtained by reacting these tertiary amino group-containing monomers with quaternizing agents such as methyl chloride, benzyl chloride, dimethyl sulfate, and epichlorohydrin. Among these, examples of monomers having quaternary ammonium salts include (meth)acryloyloxyethyl trimethyl ammonium chloride and (meth)acryloyloxyethyl dimethyl benzyl ammonium chloride. Two or more of these can be combined. The amount of cationic monomer is 70 to 99% by mass, preferably 75 to 98% by mass, of the total monomers. If the amount of cationic monomer is small, the adsorption to the pulp is reduced, and the turbidity removal effect, the effect of reducing the moisture content of the pulp sheet, and the effect of increasing paper strength are reduced. Furthermore, if the amount of cationic monomer is too high, the amount of hydrophobic monomer will be reduced, resulting in insufficient formation of hydrophobic associations and reduced effectiveness.

Here, the hydrophobic monomer means a monomer having a solubility of 2% by mass or less in water at 20°C. Examples of hydrophobic monomers include methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, octyl (meth)acrylate, stearyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, dodecyl (meth)acrylate, octadecyl (meth)acrylate, styrene, ethylstyrene, and the like. Two or more of these can also be combined. The amount of hydrophobic monomer is 1 to 30% by mass, preferably 2 to 25% by mass, based on the total monomers. If the amount of hydrophobic monomer is small, the formation of hydrophobic associations becomes insufficient, and the turbidity removal effect, the effect of reducing the moisture content of the pulp sheet, and the effect of increasing paper strength are reduced. If the amount of hydrophobic monomer is large, the amount of cationic monomer is small, and the interaction with the pulp is reduced, resulting in a reduced effect.

The polymer of the present invention may further contain nonionic monomers, anionic monomers, crosslinkable monomers, etc. as polymerization components. The total amount of these is preferably 10% by mass or less of the total monomers.

Nonionic monomers include acrylamide, dimethylacrylamide, diethylacrylamide, isopropylacrylamide, hydroxyethylacrylamide, vinylpyrrolidone, vinylformamide, glycerol (meth)acrylate, hydroxyethyl (meth)acrylate, etc. Two or more of these can also be combined.

Examples of anionic monomers include (meth)acrylic acid, itaconic acid, maleic acid, styrenesulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, and salts thereof. Two or more of these can also be combined.

Examples of crosslinkable monomers include methylenebisacrylamide, ethylene glycol di(meth)acrylate, N-methylolacrylamide, triallyl isocyanate, and divinylbenzene. Two or more of these can be combined. The addition rate of the crosslinkable monomer is preferably 1% by mass or less based on the total monomers.

A surfactant can be used during polymerization. The surfactant is a substance having a hydrophilic group and a hydrophobic group in the molecule, and examples of the surfactant include polyoxyalkylene alkyl ethers, polyoxyethylene sorbitan fatty acid esters such as polyoxyethylene sorbitan monooleate and polyoxyethylene sorbitan trioleate, polyoxyethylene alkyl ethers such as polyoxyethylene cetyl ether, polyoxyethylene oleyl ether and polyoxyethylene lauryl ether, sorbitan fatty acid esters such as sorbitan monooleate and sorbitan monostearate, and polyoxyethylene higher alcohol ethers such as sodium dodecyl sulfate, sodium dodecylbenzenesulfonate, naphthalenesulfonate-formalin condensate and pentaoxyethylene oleyl alcohol ether. Two or more of these can be combined. Polymerization in water in the presence of a surfactant has the effect of finely dispersing the monomers, promoting copolymerization. If the amount of surfactant is small, the effect of finely dispersing the monomers is small, and if the amount is too large, it will cause foaming when dissolved and used. The surfactant addition rate is 0.01% to 5% by mass, preferably 0.05% to 3% by mass, and more preferably 0.1% to 1% by mass, based on the total monomers.

In the present invention, a chain transfer agent can be used. Examples of the chain transfer agent include alkyl mercaptans, thioglycolic acid and its esters, isopropyl alcohol, allyl alcohol, allylamine, sodium hypophosphite, and the like. Also included are monomers such as methallylsulfonates, such as sodium methallylsulfonate, potassium methallylsulfonate, and ammonium methallylsulfonate.

Examples of the polymerization initiator include azo-based polymerization initiators such as 2,2'-azobis[2-(5-methyl-imidazolin-2-yl)propane] dihydrochloride, 2,2'-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride, and 2,2'-azobis-2-amidinopropane dihydrochloride. Other examples include persulfates such as sodium persulfate, potassium persulfate, and ammonium persulfate, and peroxides such as hydrogen peroxide and benzoyl peroxide. These can be used alone, but can also be used as redox-based polymerization initiators in combination with reducing agents such as sulfites and hydrogen sulfites. The addition rate of the polymerization initiator is 0.01% to 2% by mass, preferably 0.1 to 1% by mass, based on the total monomers.

The polymerization reaction is usually carried out at a temperature of 30°C to 100°C for a time of 0.5 to 20 hours. The concentration of the resulting polymer is usually 5 to 50% by mass.

According to the present invention, it is possible to obtain a papermaking additive made of a polymer that has excellent turbidity removal effects, effects of reducing the moisture content of pulp sheets, and effects of increasing paper strength.

The obtained polymer preferably has a viscosity of 15 to 150 mPa·s in a 1% by weight aqueous solution of the polymer. The viscosity is measured with a B-type viscometer at 60 rpm and 25°C. If the viscosity is less than 15 mPa·s, the effect is insufficient. If the viscosity is more than 150 mPa·s, the solubility decreases and handling becomes difficult. As the B-type viscometer, a general-purpose product such as the B8M model or TVB-10M model manufactured by Toki Sangyo Co., Ltd. is appropriately used. If the viscosity is 100 mPa·s or less, a No. 1 rotor is used.

The location of addition of the polymeric papermaking additive of the present invention will be described below.
The location of addition can be the raw material for papermaking upstream of the papermaking process, where the pulp dry solids concentration is 2.0% by mass or more before papermaking. Pitches, anionic substances, and turbidity components derived from waste paper, coating breaks, and resins in the raw material for papermaking cause various pitch troubles such as paper stains, defects, paper breaks, and dirt on the papermaking machine. In particular, it is considered that the complex involvement and growth of turbidity components and micro-pitch are major factors in pitch troubles, and it is necessary to treat them. For this purpose, the polymer of the present invention can be added to the raw material for papermaking to treat them by the pitch control effect.

In the papermaking process, high-concentration papermaking raw material with a pulp dry solids concentration of 2.0% by mass or more is diluted with white water or fresh water just before the papermaking machine to a papermaking raw material with a pulp dry solids concentration of less than 2.0% by mass. Generally, it is diluted to 0.5 to 1.5% by mass, and these are called inlet raw material or headbox raw material. The polymer of the present invention can be added to these raw materials (hereinafter referred to as inlet raw material). The addition location is before or after the fan pump or before or after the screen, which are shearing processes.
Since the polymer of the present invention has a pitch control effect, a drainage improvement effect (as well as a water squeezing improvement effect), and a paper strength enhancement effect, the polymer is not limited to the addition location of conventional pitch control agents, drainage improvers, and paper strength enhancers, and can be applied to any of the inlet raw materials diluted with a pulp dry solids concentration of 2.0 mass% or more upstream of the papermaking process, and the inlet raw materials diluted with a papermaking raw material having a pulp dry solids concentration of less than 2.0 mass%. In order to maximize the effect of the polymer of the present invention, which has a pitch control effect, a drainage improvement effect (as well as a water squeezing improvement effect), and a paper strength enhancement effect, it is preferable to add it to the inlet raw materials before or after the fan pump closer to the wire part or before or after the screen.

The types of paper to which the polymer-based papermaking additive of the present invention is applied include newsprint, wood-free printing paper, medium-quality printing paper, gravure printing paper, PPC paper, coated base paper, lightly coated paper, packaging paper, liner and core base paper boards, etc. Among these, liner and core base paper boards, which are more required to have the combined effects of pitch suppression, drainage improvement, and paper strength enhancement, are preferred. The addition rate is 0.01 to 1 mass% of the polymer pure content relative to the dry solid content of the pulp, preferably 0.01 to 0.5 mass%. In addition, the additive can be used in combination with other papermaking chemicals such as paper strength enhancers, sizing agents, aluminum sulfate, pitch control agents, retention aids, and drainage aids.

The present invention will now be described in more detail with reference to the following examples.

Example 1
In a 500 mL four-neck flask, 1.0 g of styrene, 40.2 g of dimethylaminoethyl methacrylate, 25.5 g of 35% by mass hydrochloric acid, 183.4 g of demineralized water, 0.1 g of sodium dodecyl sulfate, and 0.05 g of 2,2'-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride (VA-044 manufactured by Wako Pure Chemical Industries, Ltd.) were charged and nitrogen gas was passed through while stirring at 150 rpm. After 30 minutes, the temperature was raised to 50°C and maintained for 3 hours. Then, the temperature was maintained at 70°C for 2 hours. Then, the mixture was cooled to obtain an aqueous polymer solution. The viscosity of the 1% by mass aqueous solution of the obtained polymer was 45.7 mPa·s. The results are shown in Table 1.

Example 2
In a 500 mL four-neck flask, 2.5 g of styrene, 39.0 g of dimethylaminoethyl methacrylate, 24.7 g of 35% by mass hydrochloric acid, 183.3 g of demineralized water, 0.1 g of sodium dodecyl sulfate, and 0.05 g of 2,2'-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride (VA-044 manufactured by Wako Pure Chemical Industries, Ltd.) were charged and nitrogen gas was passed through while stirring at 150 rpm. After 30 minutes, the temperature was raised to 50°C and maintained for 3 hours. Then, the temperature was maintained at 70°C for 2 hours. Then, the mixture was cooled to obtain an aqueous polymer solution. The viscosity of the 1% by mass aqueous solution of the obtained polymer was 41.9 mPa·s. The results are shown in Table 1.

Example 3
In a 500 mL four-neck flask, 5.0 g of styrene, 36.9 g of dimethylaminoethyl methacrylate, 23.4 g of 35% by mass hydrochloric acid, 184.4 g of demineralized water, 0.1 g of sodium dodecyl sulfate, and 0.05 g of 2,2'-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride (VA-044 manufactured by Wako Pure Chemical Industries, Ltd.) were charged and nitrogen gas was passed through while stirring at 150 rpm. After 30 minutes, the temperature was raised to 50°C and maintained for 3 hours. Then, the temperature was maintained at 70°C for 2 hours. Then, the mixture was cooled to obtain an aqueous polymer solution. The viscosity of the 1% by mass aqueous solution of the obtained polymer was 25.7 mPa·s. The results are shown in Table 1.

Example 4
In a 500 mL four-neck flask, 12.5 g of styrene, 30.8 g of dimethylaminoethyl methacrylate, 19.5 g of 35% by mass hydrochloric acid, 184.2 g of demineralized water, 0.5 g of sodium dodecyl sulfate, and 0.1 g of 2,2'-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride (VA-044 manufactured by Wako Pure Chemical Industries) were charged and nitrogen gas was passed through while stirring at 150 rpm. After 30 minutes, the temperature was raised to 50°C and maintained for 3 hours. Then, the temperature was maintained at 70°C for 2 hours. Then, the mixture was cooled to obtain an aqueous polymer solution. The viscosity of the 1% by mass aqueous solution of the obtained polymer was 21.9 mPa·s. The results are shown in Table 1.

Example 5
In a 500 mL four-neck flask, 15.0 g of styrene, 28.8 g of dimethylaminoethyl methacrylate, 18.4 g of 35% by mass hydrochloric acid, 187.2 g of demineralized water, 0.5 g of sodium dodecyl sulfate, and 0.05 g of 2,2'-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride (VA-044 manufactured by Wako Pure Chemical Industries, Ltd.) were charged and nitrogen gas was passed through while stirring at 150 rpm. After 30 minutes, the temperature was raised to 50°C and maintained for 3 hours. Then, the temperature was maintained at 70°C for 2 hours. Then, the mixture was cooled to obtain an aqueous polymer solution. The viscosity of the 1% by mass aqueous solution of the obtained polymer was 21.6 mPa·s. The results are shown in Table 1.

Example 6
In a 500 mL four-neck flask, 1.0 g of dodecyl methacrylate, 61.3 g of 80% by mass methacryloyloxyethyl trimethylammonium chloride, 187.4 g of demineralized water, 0.5 g of sodium dodecyl sulfate, 0.05 g of 2,2'-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride (VA-044 manufactured by Wako Pure Chemical Industries), and 0.075 g of sodium hypophosphite were charged and nitrogen gas was passed through while stirring at 150 rpm. After 30 minutes, the temperature was raised to 50°C and maintained for 3 hours. Then, the temperature was maintained at 70°C for 2 hours. Then, the mixture was cooled to obtain an aqueous polymer solution. The viscosity of the 1% by mass aqueous solution of the obtained polymer was 24.6 mPa·s. The results are shown in Table 1.

(Example 7)
In a 500 mL four-neck flask, 0.5 g of dodecyl methacrylate, 61.9 g of 80% by mass methacryloyloxyethyl trimethylammonium chloride, 187.3 g of demineralized water, 0.5 g of sodium dodecyl sulfate, 0.05 g of 2,2'-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride (VA-044 manufactured by Wako Pure Chemical Industries), and 0.091 g of sodium hypophosphite were charged and nitrogen gas was passed through while stirring at 150 rpm. After 30 minutes, the temperature was raised to 50°C and maintained for 3 hours. Then, the temperature was maintained at 70°C for 2 hours. Then, the mixture was cooled to obtain an aqueous polymer solution. The viscosity of the 1% by mass aqueous solution of the obtained polymer was 18.6 mPa·s. The results are shown in Table 1.

(Example 8)
In a 500 mL four-neck flask, 0.5 g of 80% by mass acrylic acid, 0.5 g of butyl acrylate, 0.5 g of hydroxyethyl methacrylate, 0.5 g of methyl methacrylate, 1.0 g of styrene, 38.6 g of dimethylaminoethyl methacrylate, 24.5 g of 35% by mass hydrochloric acid, 183.3 g of demineralized water, 0.1 g of sodium dodecyl sulfate, and 0.05 g of 2,2'-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride (VA-044 manufactured by Wako Pure Chemical Industries) were charged and nitrogen gas was passed through while stirring at 150 rpm. After 30 minutes, the temperature was raised to 50°C and maintained for 3 hours. Then, the temperature was maintained at 70°C for 2 hours. Then, the mixture was cooled to obtain an aqueous polymer solution. The viscosity of the 1% by mass aqueous solution of the obtained polymer was 106.1 mPa·s. The results are shown in Table 1.

(Comparative Example 1)
In a 500 mL four-neck flask, 40.9 g of dimethylaminoethyl methacrylate, 26.0 g of 35% by mass hydrochloric acid, 182.3 g of demineralized water, and 0.05 g of 2,2'-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride (VA-044 manufactured by Wako Pure Chemical Industries, Ltd.) were charged and nitrogen gas was passed through while stirring at 150 rpm. After 30 minutes, the temperature was raised to 50°C and maintained for 3 hours. Then, the temperature was maintained at 70°C for 2 hours. Then, the mixture was cooled to obtain an aqueous polymer solution. The viscosity of the 1% by mass aqueous solution of the obtained polymer was 43.8 mPa·s. The results are shown in Table 1.

(Comparative Example 2)
In a 500 mL four-neck flask, 20.0 g of styrene, 24.7 g of dimethylaminoethyl methacrylate, 15.7 g of 35% by mass hydrochloric acid, 188.3 g of demineralized water, 0.5 g of sodium dodecyl sulfate, and 0.05 g of 2,2'-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride (VA-044 manufactured by Wako Pure Chemical Industries, Ltd.) were charged and nitrogen gas was passed through while stirring at 150 rpm. After 30 minutes, the temperature was raised to 50°C and maintained for 3 hours. Then, the temperature was maintained at 70°C for 2 hours. Then, the mixture was cooled to obtain an aqueous polymer solution. The viscosity of the 1% by mass aqueous solution of the obtained polymer was 23.4 mPa·s. The results are shown in Table 1.

(Comparative Example 3)
In a 500 mL four-neck flask, 62.5 g of 80% by mass methacryloyloxyethyl trimethylammonium chloride, 187.5 g of demineralized water, and 0.1 g of 2,2'-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride (VA-044 manufactured by Wako Pure Chemical Industries, Ltd.) were charged and nitrogen gas was passed through while stirring at 150 rpm. After 30 minutes, the temperature was raised to 50°C and maintained for 3 hours. Then, the temperature was maintained at 70°C for 2 hours. Then, the mixture was cooled to obtain an aqueous polymer solution. The viscosity of the 1% by mass aqueous solution of the obtained polymer was 16.4 mPa·s. The results are shown in Table 1.

カチオン性単量体；ＤＭＭ：ジメチルアミノエチルメタクリレート、
ＤＭＣ：メタクリロイルオキシエチルトリメチルアンモニウムクロライド
疎水性単量体；Ｓｔ：スチレン、ＤＤＭ：ドデシルメタクリレート、ＭＭＡ：メチルメタクリレート、ＢｕＡ：ブチルアクリレート
ノ二オン性単量体；ＨＥＭＡ：ヒドロキシエチルメタクリレート
アニオン性単量体；ＡＡＣ：アクリル酸 (Table 1)

Cationic monomer; DMM: dimethylaminoethyl methacrylate,
DMC: methacryloyloxyethyltrimethylammonium chloride hydrophobic monomer; St: styrene, DDM: dodecyl methacrylate, MMA: methyl methacrylate, BuA: butyl acrylate nonionic monomer; HEMA: hydroxyethyl methacrylate anionic monomer; AAC: acrylic acid

In addition, commercially available pitch control agents, drainage improvers, and paper strength agents were prepared as comparative polymer samples. Their compositions and physical properties are shown in Table 2.

形態；ＡＱ：水溶液重合体、ＤＲ：塩水液中分散重合液
０．５質量％塩水溶液粘度：４質量％食塩水中に高分子濃度が０．５質量％になるように溶解したときの２５℃において測定した粘度（ｍＰａ・ｓ）。 (Table 2)

Form: AQ: aqueous solution polymer, DR: polymer dispersion in saline solution 0.5% by mass saline solution Viscosity: viscosity (mPa·s) measured at 25° C. when dissolved in 4% by mass saline solution to give a polymer concentration of 0.5% by mass.

Using the polymer samples in Table 1 and the commercially available samples in Table 2, we conducted a turbidity removal test, a pulp sheet moisture content measurement test, and a paper strength enhancement effect test. As a paper material, recycled cardboard was beaten with a Niagara beater to a beating degree of 320 mL, and used as a pulp slurry with a pulp concentration of 2% by mass (pH 7.3, electrical conductivity 117.1 mS/m).

(Example 1) (Turbidity removal test)
To 100 g of a slurry having a pulp concentration of 2% by mass, Latex Bond SP210N was added as a simulated pitch to give a concentration of 167 ppm relative to the liquid, and the mixture was stirred at 200 rpm for 30 seconds, and then the polymer sample of the present invention shown in Table 1 was added to give a concentration of 0.05% by mass (pure polymer content) relative to the pulp solid content, and the mixture was stirred at 200 rpm for 1 minute. The mixture was then filtered through Whatman No. 41 filter paper, and the turbidity of the filtrate was measured using a HACH turbidimeter 2100P. The results are shown in Table 3.

Comparative Test Example 1
Using the same pulp slurry as in Example 1, tests similar to those in Example 1 were carried out using a polymer sample outside the scope of the present invention, a commercially available pitch control agent, and a commercially available paper strength agent. Tests were also carried out without the addition of any polymer sample. The results are shown in Table 3.

(Test Example 2) (Pulp Sheet Moisture Content Measurement Test)
A drainage test was carried out using a dynamic drainage tester (DDA, manufactured by Matsubo). The waste cardboard pulp slurry diluted to a pulp concentration of 1% was placed in a DDA stirring tank with a 315 mesh wire attached to the bottom. The polymer sample of the present invention in Table 1 was added so as to be 0.05% by mass (pure polymer content) relative to the pulp solid content, and after stirring at a stirring speed of 800 rpm for 30 seconds, the paper material was sucked under a reduced pressure of 300 mBar to form a sheet on the wire. The sheet was taken out, its weight was measured, and it was further dried in a 105°C air blower for about 15 hours, after which its weight was measured and the sheet moisture content was calculated. The results are shown in Table 3.

Comparative Test Example 2
Using the same pulp slurry as in Example 2, tests similar to those in Example 2 were carried out using a polymer sample outside the scope of the present invention, a commercially available drainage improver, and a commercially available paper strength enhancer. Tests were also carried out without the addition of any polymer sample. The results are shown in Table 3.

(Test Example 3) (Paper Strength Enhancement Effect Test)
The polymer sample in Table 1 of the present invention was added to 500 mL of the waste cardboard pulp slurry diluted to a pulp concentration of 1% by mass so that the polymer sample was 0.1% by mass (pure polymer content) relative to the pulp solid content, and after stirring at 800 rpm for 1 minute, paper was made using a TAPPI standard papermaking machine (using 80 mesh wire), followed by pressing at a pressure of 410 kPa for 5 minutes, and then drying at 105 ° C. for 3 minutes using a rotary drum dryer. The paper was conditioned for 24 hours under conditions of a temperature of 23 ° C. and a humidity of 50%, to obtain a paper with a basis weight of 80 g / m ^2. The compressive strength of the obtained paper was measured and expressed as a specific compressive strength. The compressive strength was measured using a short span compression tester (L & W, Compressive Strength Tester STFI) according to JIS P 8126. The results are shown in Table 3.

Comparative Test Example 3
Using the same pulp slurry as in Example 3, tests similar to those in Example 3 were carried out using a polymer sample outside the scope of the present invention, a commercially available pitch control agent, and a commercially available paper strength agent. Tests were also carried out without the addition of any polymer sample. The results are shown in Table 3.

(Table 3)

When a papermaking additive consisting of the polymer of the present invention was added, the same or better turbidity reduction effect, sheet moisture content reduction effect, and paper strength enhancement effect were obtained compared to polymers outside the scope of the present invention and commercially available products, and the function as a pitch control agent, drainage improver, and paper strength enhancer was confirmed.

The pitch control effect, sheet moisture content reduction effect, and paper strength enhancement effect of the polymer sample of the present invention were equal to or greater than those of commercially available products having each function, and it was confirmed that these effects were combined. Even if the polymers and commercially available products outside the scope of the present invention had excellent effects in any one of the pitch control effect, sheet moisture content reduction effect, and paper strength enhancement effect, no significant effects were observed in the other functions. By using the polymer of the present invention as a papermaking additive, it has multiple functions by adding one agent, and is extremely useful as a papermaking additive.

Claims (2)

A method for preventing pitch troubles, comprising adding a papermaking additive consisting of a polymer obtained by polymerizing a monomer mixture containing 70 to 99% by mass of a cationic monomer and 1 to 30% by mass of a hydrophobic monomer to a papermaking raw material having a pulp dry solids concentration of 2.0% by mass or more upstream of the papermaking process before papermaking . 2. The method for preventing pitch trouble according to claim 1, wherein the polymer has a viscosity (25° C.) of 15 to 150 mPa·s when dissolved in a solution of 1% by mass and measured at a rotation speed of 60 rpm using a B-type viscometer .