Papermaking additive, method for producing papermaking additive, and paper

Abstract

The present invention relates to a papermaking additive, a method for producing a papermaking additive, and paper. The present invention provides a papermaking additive which has less viscosity increase after long-term storage and exhibits excellent drainage and paper strength effects. A papermaking additive comprising a (meth)acrylamide-based polymer, the (meth)acrylamide-based polymer having starch (a1), (meth)acrylamide (a2), a polymerizable monomer having an amino group (a3), a polymerizable monomer having a carboxyl group (a4), and a polymerizable monomer having a sulfonic acid group (a5) as essential constituent components, the starch (a1) being two or more selected from the group consisting of unmodified starch, oxidized starch, esterified starch, etherified starch, amidated starch, cationized starch, amphoteric starch, and crosslinked starch.

Description

TECHNICAL FIELD

[0001] The present application relates to a papermaking additive, a method for producing a papermaking additive, and paper. BACKGROUND

[0002] A papermaking additive is a chemical agent added to a pulp slurry during papermaking, and is used mainly to improve the strength, drainage, and retention of chemicals or fine fibers in paper.

[0003] Among these, (meth)acrylamide-based polymers (Patent Document 1, Patent Document 2) or starch have been mainly used as papermaking additives for improving the strength of paper. (Meth)acrylamide-based polymers have high adhesion to pulp and exhibit excellent paper strength effects even at a small amount of addition, but are more expensive than starch. On the other hand, starch is inexpensive and a (biomass) raw material having biodegradability, but has low adhesion to pulp, and thus needs to be added in a large amount relative to the non-volatile components of the pulp in order to exhibit the same high paper strength effects as (meth)acrylamide-based polymers.

[0004] Therefore, as a means for obtaining a papermaking additive that is relatively inexpensive and has excellent paper strength effects by effectively utilizing the respective advantages of (meth)acrylamide-based polymers and starch, these materials have been reacted.

[0005] As a specific example, a papermaking additive obtained by graft polymerization of a monomer mixture composed of only a specific amount of each of dialkylaminoalkyl (meth)acrylamide, (meth)acrylic acid, and (meth)acrylamide, and starch or modified starch is known (Patent Document 3). However, in the polymer obtained by this polymerization method, the starch is chronologically aged, and thus there is a problem in terms of quality in that the viscosity easily increases (poor storage stability).

[0006] [Related Art Documents]

[0007] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-251252

[0009] [Patent Document 2] Japanese Patent Application Laid-Open No. 2011-168948

[0010] [Patent Document 3] Japanese Patent Application Laid-Open No. Show 63-219696 SUMMARY

[0011] [Problems to be Solved by the Invention]

[0012] The present invention provides a papermaking additive which has less viscosity increase after long-term storage and exhibits excellent drainage and paper strength effects.

[0013] [Technical means for solving the problem]

[0014] The present inventors have conducted intensive studies by using two or more kinds of starches in combination and appropriately adjusting the monomer composition, and thus completed the present invention. That is, the present invention relates to a papermaking additive, a method for producing a papermaking additive, and paper.

[0015] 1. A papermaking additive comprising a (meth) acrylamide-based polymer, the (meth) acrylamide-based polymer being composed of starches (al), a (meth) acrylamide (a2), a polymerizable monomer having an amino group (a3), a polymerizable monomer having a carboxyl group (a4), and a polymerizable monomer having a sulfonic acid group (a5) as essential components, the starches (al) being two or more kinds selected from the group consisting of unmodified starch, oxidized starch, esterified starch, etherified starch, amidated starch, cationized starch, amphoteric starch, and crosslinked starch.

[0016] 2. The papermaking additive according to the preceding item 1, wherein the (al) component comprises: a starch (al-1) which is one kind selected from the group consisting of esterified starch and amphoteric starch; and a starch (al-2) which is one kind selected from the group consisting of unmodified starch, oxidized starch, and cationized starch.

[0017] 3. The papermaking additive according to the preceding item 1 or 2, wherein the ratio of the use amount of the (al) component to the total use amount of the (a2) component to the (a5) component, based on the nonvolatile component, is [(al) / {(a2)+(a3)+(a4)+(a5)}] = 5 / 95 to 45 / 55.

[0018] 4. The papermaking additive according to any one of the preceding items 1 to 3, wherein, when the total use amount of the (a2) component to the (a5) component is set to 100% by weight, the (a3) component is 1.5% by weight to 35% by weight, the (a4) component is 1% by weight to 15% by weight, and the (a5) component is 0.5% by weight to 8% by weight.

[0019] 5. The papermaking additive according to any one of the preceding items 1 to 4, wherein the essential components further comprise a polymerizable monomer having a crosslinkable group (a6).

[0020] 6. The papermaking additive according to any one of the preceding items 1 to 5, wherein the weight average molecular weight of the (meth) acrylamide-based polymer is 1.5 million to 7 million.

[0021] 7. The papermaking additive according to any one of paragraphs 1 to 6, wherein the maximum turbidity of a 1% by weight aqueous solution of the (meth)acrylamide polymer prepared by diluting with water having a conductivity of 3 mS / cm·25°C prepared by ion-exchange water and sodium sulfate is 50 to 1000 nephelometric turbidity units (NTU) to pH 3 to 9.

[0022] 8. A method for manufacturing an additive for papermaking, comprising the method for manufacturing an additive for papermaking according to any one of the preceding items 1 to 7, and comprising the step of polymerizing a constituent component having (a1), (a2), (a3), (a4) and (a5) as essential components in the presence of component (a1) to obtain a (meth)acrylamide polymer.

[0023] 9. The method for manufacturing the paper additive according to item 8 above, wherein the constituent components further include a polymeric monomer (a6) having a crosslinking group.

[0024] 10. A paper comprising papermaking additives according to any one of the preceding items 1 to 7.

[0025] [The effects of the invention]

[0026] The papermaking additive according to the present invention exhibits minimal viscosity increase during long-term storage and demonstrates excellent water-filtration and paper strength effects. Attached Figure Description

[0027] Figure 1 This is a graph showing the pH-turbidity distribution as a "single peak".

[0028] Figure 2 This is a graph showing the pH-turbidity distribution as a "bimodal" pattern. Detailed Implementation

[0029] The papermaking additive of the present invention comprises a (meth)acrylamide polymer, wherein the (meth)acrylamide polymer has starch (a1) (hereinafter referred to as (a1) component), (meth)acrylamide (a2) (hereinafter referred to as (a2) component), an amino-containing polymerizable monomer (a3) ​​(hereinafter referred to as (a3) ​​component), a carboxyl-containing polymerizable monomer (a4) (hereinafter referred to as (a4) component), and a sulfonic acid-containing polymerizable monomer (a5) (hereinafter referred to as (a5) component) as essential constituent components, wherein the starch (a1) is selected from two or more of the group consisting of unmodified starch, oxidized starch, esterified starch, etherified starch, amidated starch, cationic starch, amphoteric starch, and cross-linked starch.

[0030] (a1) the component is two or more kinds of starch selected from the group consisting of unmodified starch, oxidized starch, esterified starch, etherified starch, amidated starch, cationized starch, amphoteric starch, and crosslinked starch. When two or more kinds selected from the group are used as the (a1) component, the obtained papermaking additive exhibits excellent storage stability, and when the obtained papermaking additive is added to a pulp slurry, the pulp is moderately coagulated by the (meth)acrylamide-based polymer contained in the additive, thereby also exhibiting excellent paper strength effects.

[0031] As the unmodified starch, for example, corn starch, waxy corn starch, potato starch, tapioca starch, wheat starch, rice starch, sago starch, and the like can be exemplified.

[0032] As the oxidized starch, a starch obtained by treating the unmodified starch with an oxidizing agent can be exemplified.

[0033] As the oxidizing agent, for example, halogens such as chlorine, bromine, hypochlorite, hypobromite, and the like can be exemplified. In addition, as the salt, alkali metal salts such as potassium, sodium, and the like can be exemplified.

[0034] As the esterified starch, for example, inorganic acid esterified starches such as nitric acid esterified starch, sulfuric acid esterified starch, phosphoric acid esterified starch, urea-phosphoric acid esterified starch, and the like; organic acid esterified starches such as acetoacetic acid esterified starch, acetic acid esterified starch, xanthic acid-acetic acid esterified starch, succinic acid esterified starch, maleic anhydride esterified starch, fumaric acid anhydride esterified starch, and the like; and the like can be exemplified.

[0035] As the etherified starch, for example, alkyl etherified starches such as methyl etherified starch, ethyl etherified starch, propyl etherified starch, and the like; hydroxyalkyl etherified starches such as hydroxymethyl etherified starch, hydroxyethyl etherified starch, hydroxypropyl etherified starch, hydroxybutyl etherified starch, and the like; carboxymethyl etherified starch, allyl etherified starch, and the like can be exemplified.

[0036] As the amidated starch, for example, carbamoyl ethylated starch, and the like can be exemplified.

[0037] The cationized starch is a starch obtained by treating the unmodified starch with a compound having a cationic group. As the compound having a cationic group, for example, halogenated ammonium such as 2-diethylaminoethylammonium chloride, 2,3-epoxypropyltrimethylammonium chloride, and the like can be exemplified.

[0038] The amphoteric starch is a starch obtained by treating the unmodified starch with a compound having a cationic group and a compound having an anionic group, or a compound having both a cationic group and an anionic group, that is, a starch having both a cationic group and an anionic group. Further, among the amphoteric starches, there are amphoteric starches having a phosphate group and amphoteric starches not having the ester group.

[0039] As the crosslinked starch, for example, there can be mentioned: phosphoric acid crosslinked starch, acetylated phosphoric acid crosslinked starch, adipic acid crosslinked starch, acetylated adipic acid crosslinked starch, formaldehyde crosslinked starch, acrolein crosslinked starch, epichlorohydrin crosslinked starch, and the like.

[0040] As the (al) component, a starch class subjected to a degradation treatment can also be used. The starch class subjected to a degradation treatment can be obtained by allowing a degradation treatment agent to act on an unmodified starch, an oxidized starch, an esterified starch, an etherified starch, an amidated starch, a cationized starch, an amphoteric starch, or a crosslinked starch and heating and stirring at 60°C to 100°C for 30 minutes to 60 minutes.

[0041] As the degradation treatment agent, for example, there can be mentioned: hypochlorite, peroxydisulfate (ammonium persulfate, potassium persulfate, sodium persulfate, and the like), hydrogen peroxide and the like inorganic peroxide; bacteria, enzymes such as α-amylase, and the like. These can be used alone or two or more kinds can be combined. Further, in the case of using hydrogen peroxide, at least one water-soluble metal salt of iron sulfate and copper sulfate can also be combined.

[0042] Further, as to the starch class subjected to a degradation treatment obtained by the method, it is defined as in Table 1 according to the classification of the raw material used.

[0043] [Table 1]

[0044] Raw materials used Starch name produced Unmodified starch Degraded starch Oxidized starch Degraded oxidized starch Esterified starch Degraded esterified starch Etherified starch Degraded etherified starch Amidated starch Degraded amidated starch Cationic starch Degraded cationic starch Amphoteric starch Degraded amphoteric starch Crosslinked starch Degraded crosslinked starch

[0045] As the (al) component, a starch class subjected to a degradation treatment can also be used. The starch class subjected to a degradation treatment can be obtained by allowing a degradation treatment agent to act on an unmodified starch, an oxidized starch, an esterified starch, an etherified starch, an amidated starch, a cationized starch, an amphoteric starch, or a crosslinked starch and heating and stirring at 60°C to 100°C for 30 minutes to 60 minutes.

[0046] As the physical properties of the (a1) component, the viscosity of a paste solution of the (a1) component having a nonvolatile component concentration of 20% by weight at a temperature of 25°C is preferably 5 mPa-s to 5000 mPa-s, more preferably 10 mPa-s to 2500 mPa-s. If the (a1) component having the viscosity is used, it is easy to react with the constituent components such as (meth) acrylamide, and as a result, the papermaking additive obtained exhibits excellent storage stability, in addition, the turbidity of the papermaking additive is easily increased, and when added to the pulp slurry, the pulp is moderately coagulated by the (meth) acrylamide-based polymer contained in the additive, and thus exhibits excellent paper strength effects. Furthermore, the paste solution of the (a1) component having a concentration of 20% by weight refers to a liquid obtained by diluting the (a1) component to a concentration of 20% by weight with a solvent (particularly preferably water) described later, and heating and stirring at a temperature of 90°C for 1 hour. In addition, the viscosity is a value measured using a B-type viscometer.

[0047] Of these, in terms of the papermaking additive exhibiting excellent storage stability, as the (a1) component, it is preferable to contain: a starch (a1-1) (hereinafter referred to as the (a1-1) component) which is one selected from the group consisting of esterified starch and amphoteric starch; and a starch (a1-2) (hereinafter referred to as the (a1-2) component) which is one selected from the group consisting of unmodified starch, oxidized starch, and cationized starch.

[0048] As the use ratio of the (a1-1) component and the (a1-2) component, in terms of the papermaking additive exhibiting excellent storage stability, it is preferable that the (a1-1) / (a1-2) = 5 / 95 to 95 / 5, more preferably 10 / 90 to 90 / 10, and further preferably 20 / 80 to 80 / 20, in terms of the weight of the nonvolatile components.

[0049] Furthermore, as the (a1-1) component, in terms of the papermaking additive exhibiting excellent storage stability, it is more preferable to be a starch having a phosphate group.

[0050] As such an (a1-1) component (i.e., a starch having a phosphate group), phosphoric acid esterified starch (including amphoteric starch having a phosphate group, the same applies hereafter), urea-phosphoric acid esterified starch, and the like can be exemplified. These can be used alone or in combination of two or more. Of these, in terms of the papermaking additive exhibiting excellent storage stability, it is more preferable to be amphoteric starch having a phosphate group and urea-phosphoric acid esterified starch.

[0051] In addition, as the (a1-2) component, it is preferable to be oxidized starch and degradation-treated cationized starch.

[0052] Although the details are not clear, the following describes a mechanism showing excellent storage stability of the papermaking additive of the present application.

[0053] With respect to the viscosity increase of the present application that occurs during long-term storage, it is considered that it occurs due to aging or thixotropy of the starch.

[0054] With respect to the (meth)acrylamide-based polymer that is polymerized in the presence of the starch having a phosphate group, although the viscosity increase due to aging of the starch can be inhibited, it can increase in viscosity over time because strong thixotropy can occur. On the other hand, with respect to the (meth)acrylamide-based polymer that is polymerized in the presence of the starch not having a phosphate group, although the aging of the starch easily proceeds rapidly, it has a tendency not to exhibit thixotropy compared to the starch having a phosphate group.

[0055] Therefore, it is presumed that if the starch having a phosphate group and the starch not having a phosphate group are used together, both of the aging and the occurrence of thixotropy, which are factors that cause the viscosity increase, are inhibited, and excellent storage stability is shown even during long-term storage. It is considered that in the case where the (a1-1) component and the (a1-2) component having a phosphate group are used together as the (a1) component, the above-described presumed mechanism particularly easily occurs, and thus excellent storage stability is shown.

[0056] Further, as the use amount of the starch other than the (a1-1) component and the (a1-2) component as the third or more components (in order, the (a1-3) component, the (a1-4) component,..., the (a1-n) component (n: a positive integer)), each is preferably 5% by weight or less, and more preferably 3% by weight or less, based on 100% by weight of the entire (a1) component.

[0057] The (a2) component is a methacrylamide or an acrylamide. These can be used alone or two kinds can be combined.

[0058] The (a3) component is a polymerizable monomer having an amino group, and is a component that makes the (meth)acrylamide-based polymer well fixed to the pulp by being incorporated into the polymer. As the (a3) component, for example, a polymerizable monomer having a secondary amino group, a polymerizable monomer having a tertiary amino group, a quaternary salt of these polymerizable monomers, and the like can be exemplified.

[0059] As the polymerizable monomer having a secondary amino group, there is no particular limitation, and for example, a diallylamine or the like can be exemplified. As the polymerizable monomer having a tertiary amino group, there is no particular limitation, and for example, a (meth)acrylate having a tertiary amino group such as N,N-dimethylaminoethyl (meth)acrylate, N,N-diethylaminoethyl (meth)acrylate, or the like; a (meth)acrylamide having a tertiary amino group such as N,N-dimethylaminopropyl (meth)acrylamide, N,N-diethylaminopropyl (meth)acrylamide, or the like can be exemplified. The so-called quaternary salt of these monomers refers to a salt or the like formed by reacting the polymerizable monomer having a secondary amino group or the polymerizable monomer having a tertiary amino group with a quaternizing agent, and as the quaternary salt, a hydrochloride, a sulfate, or the like inorganic acid salt, or an acetate or the like organic acid salt can be used. In addition, as the quaternizing agent, methyl chloride, benzyl chloride, dimethyl sulfate, epichlorohydrin, or the like can be exemplified. These can be used alone or in combination of two or more. Among them, it is preferable to contain a (meth)acrylate having a tertiary amino group and / or a quaternary salt of the (meth)acrylate. Furthermore, the so-called "(meth)acrylate" refers to a methacrylate or an acrylate (the same hereinafter).

[0060] The (a4) component is a polymerizable monomer having a carboxyl group, and is a component that interacts with aluminum sulfate or the like added to a papermaking system to fix the (meth)acrylamide-based polymer in a pulp by being incorporated into the polymer. As the (a4) component, for example, (meth)acrylic acid, acrylic anhydride, itaconic acid, itaconic anhydride, fumaric acid, maleic acid, maleic anhydride, or the like can be exemplified. Furthermore, these (a4) components can be used in the form of an alkali metal salt or an ammonium salt or the like salt of sodium, potassium, or the like. These can be used alone or in combination of two or more. Among them, it is preferable to contain (meth)acrylic acid, itaconic acid, and itaconic anhydride.

[0061] The (a5) component is a polymerizable monomer having a sulfonic acid group. As the (a5) component, for example, vinylsulfonic acid, methylallylsulfonic acid, or the like can be exemplified. Furthermore, these (a5) components can be used in the form of an alkali metal salt or an ammonium salt or the like salt of sodium, potassium, or the like. These can be used alone or in combination of two or more. Among them, it is preferable to contain methylallylsulfonic acid or an alkali metal salt thereof.

[0062] As the usage amount of the (al) component to the (a5) component, the ratio of the usage amount of the (al) component to the total usage amount of the (a2) component to the (a5) component, based on the weight of the nonvolatile component, is preferably [(al) / {(a2)+(a3)+(a4)+(a5)}] = 5 / 95 to 45 / 55. By setting the ratio, when the papermaking additive is added to the pulp slurry, the pulp is moderately coagulated by the (meth) acrylamide-based polymer contained in the additive, and in addition, the polymer is also fixed to the pulp fibers to exhibit an excellent paper strength effect. In addition, in terms of the same aspect, the ratio is preferably [(al) / {(a2)+(a3)+(a4)+(a5)}] = 5 / 95 to 40 / 60, and more preferably [(al) / {(a2)+(a3)+(a4)+(a5)}] = 7.5 / 92.5 to 35 / 65.

[0063] The respective weight ratios in the case of using the (a2) component to the (a5) component as the constituent components, when the total of the (a2) component to the (a5) component is taken as 100% by weight, are as described below.

[0064] • (a2) component: generally 42% by weight to 97% by weight, preferably 54% by weight to 94.9% by weight

[0065] • (a3) component: generally 1.5% by weight to 35% by weight, preferably 3% by weight to 30% by weight

[0066] • (a4) component: generally 1% by weight to 15% by weight, preferably 1.5% by weight to 10% by weight

[0067] • (a5) component: generally 0.5% by weight to 8% by weight, preferably 0.6% by weight to 6% by weight

[0068] In addition, the constitutional component can further include a polymerizable monomer (a6) having a crosslinkable group. As the (a6) component, for example, N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N-isopropyl (meth) acrylamide, N-tert-butyl (meth) acrylamide, and the like N-alkyl (meth) acrylamides; N,N-dimethyl (meth) acrylamide, N,N-diethyl (meth) acrylamide, N,N-diisopropyl (meth) acrylamide, and the like N,N-dialkyl (meth) acrylamides; N,N'-methylenebis (meth) acrylamide, N,N'-ethylenebis (meth) acrylamide, and the like N,N'-alkylenebis (meth) acrylamides; triallyl isocyanurate, triallyl trimellitate, triallyl amine, triallyl (meth) acrylamide, and the like crosslinkable monomers having a triallyl group; 1,3,5-triacryloyl-1,3,5-triazine, 1,3,5-triacryloylhexahydro-1,3,5-triazine, and the like triazines having a (meth) acryloyl group, and the like can be exemplified. These can be used alone or in combination of two or more. Among them, it is preferable to include N,N-dimethyl (meth) acrylamide, N,N'-methylenebis (meth) acrylamide, and 1,3,5-triacryloylhexahydro-1,3,5-triazine.

[0069] In the case of using the (a6) component as the constitutional component, the use amount of the (a1) component to the (a6) component is generally in the range of [(a1) / {(a2) + (a3) + (a4) + (a5) + (a6)} ] = 5 / 95 to 45 / 55, preferably [(a1) / {(a2) + (a3) + (a4) + (a5) + (a6)} ] = 5 / 95 to 40 / 60, and more preferably [(a1) / {(a2) + (a3) + (a4) + (a5) + (a6)} ] = 7.5 / 92.5 to 35 / 65, in terms of the ratio of the use amount of the (a1) component to the total use amount of the (a2) to (a6) components, based on the nonvolatile component.

[0070] When the total of the (a2) to (a6) components is 100% by weight, the content of the (a6) component is 3% by weight or less, and preferably 2% by weight or less.

[0071] As the component, a monomer (a7) other than the components (a2) to (a6) (hereinafter, referred to as the component (a7)) can be further included. As the component (a7), there is no particular limitation, and for example, styrene, α-methylstyrene, vinyltoluene, and the like, which are polymerizable monomers having an aromatic ring; methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, n-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, cyclohexyl (meth) acrylate, and the like, which are (meth) acrylate alkyl esters; vinyl acetate, vinyl propionate, and the like, which are vinyl carboxylates; acrylonitrile and the like, which are nitriles; 2-mercaptoethanol, n-dodecyl mercaptan, and the like, which are thiols; ethanol, isopropyl alcohol, n-pentanol, and the like, which are alcohols; α-methylstyrene dimer, ethylbenzene, isopropylbenzene, cumene, and the like, which are aromatic compounds; carbon tetrachloride and the like can be exemplified. These can be used alone or in combination of two or more. In addition, when the total of the components (a2) to (a7) is set to 100% by weight, the content of the component (a7) is less than 2% by weight.

[0072] In the production of the (meth) acrylamide-based polymer, an organic acid such as citric acid, succinic acid, oxalic acid; an inorganic acid such as hydrochloric acid, sulfuric acid, phosphoric acid; an inorganic base such as sodium hydroxide, potassium hydroxide, calcium hydroxide; an antifoaming agent, an antioxidant, a preservative, a bactericide, and the like can be added. These can be used alone or in combination of two or more, and as the content thereof, 10 parts by weight or less, more preferably 8 parts by weight or less, relative to 100 parts by weight of the total of the components is preferable.

[0073] The (meth) acrylamide-based polymer of the present application can be produced to have a high weight average molecular weight and a high haze by appropriately adjusting the use amount of the components (a1) to (a6).

[0074] The (meth) acrylamide-based polymer is obtained by polymerizing the components (a1) to (a5), which are essential components, and optionally the components (a6) and (a7), and the additive in a solvent in the presence of a polymerization initiator. As the production method, for example, a step of obtaining the (meth) acrylamide-based polymer by polymerizing the components, which are essential components of the components (a1) to (a5), in the presence of the component (a1) can be exemplified. In addition, as the component (a1), a liquid obtained by dispersing the component in a solvent described later, or a substance obtained by heating the liquid to gelatinize the same, and the like can be used.

[0075] As the polymerization method, for example, a method using a dropwise polymerization method, a method using a simultaneous polymerization method (batching the monomer mixture), or a method combining the simultaneous polymerization method and the dropwise polymerization method, and the like can be exemplified.

[0076] As the solvent, water, organic solvents, and the like can be exemplified, and these can be used alone or in combination of two or more. As the organic solvent, for example, alcohols such as methanol, ethanol, n-propanol, isopropanol, n-butanol, sec-butanol, t-butanol, isobutanol, n-hexanol, n-octanol, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, diacetone alcohol, and the like; ethers such as ethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, and the like can be exemplified.

[0077] As the polymerization initiator, for example, persulfate salts such as ammonium persulfate, potassium persulfate, sodium persulfate, and the like; azo compounds such as 2,2'-azobis(2-imidazolin-2-ylpropane) hydrochloride, 2,2'-azobis[2(2-imidazolin-2-yl)propane] hydrochloride, and the like; hydrogen peroxide, and the like can be exemplified. These can be used alone or in combination of two or more. Among these, from the aspect of allowing the solution polymerization to proceed sufficiently, ammonium persulfate, potassium persulfate, 2,2'-azobis(2-imidazolin-2-ylpropane) hydrochloride are preferred. In addition, the method of adding the polymerization initiator is not particularly limited, and batch addition, separate addition, or continuous dropwise addition, and the like can be appropriately selected. In addition, the content of the polymerization initiator is not particularly limited, and is usually around 0.001 parts by weight to 5 parts by weight, and preferably around 0.01 parts by weight to 1 part by weight, relative to 100 parts by weight of the (a2) component to the (a7) component.

[0078] As the polymerization conditions, for example, the reaction temperature is usually 60°C to 95°C (preferably 70°C to 90°C). In addition, the reaction time is usually, for example, 1 hour to 6 hours (preferably 2 hours to 4 hours).

[0079] Further, the (meth)acrylamide-based polymer obtained can contain unreacted (a1) component.

[0080] From the aspect of allowing the papermaking additive to exhibit excellent storage stability, and when the papermaking additive is added to the pulp slurry, the pulp is moderately coagulated by the (meth)acrylamide-based polymer contained in the additive, and in addition, the polymer also exhibits an excellent paper strength effect by being fixed to the pulp fibers, the weight average molecular weight of the (meth)acrylamide-based polymer is preferably 1.5 million to 7 million, more preferably 1.6 million to 6.5 million, and further preferably 1.8 million to 6 million. Further, the weight average molecular weight here refers to the value obtained by the gel permeation chromatography (GPC) method.

[0081] In terms of making the papermaking additive exhibit excellent storage stability, and when the papermaking additive is added to a pulp slurry, the pulp is moderately coagulated by a (meth)acrylamide-based polymer contained in the additive, and in addition, the polymer also exhibits an excellent paper strength effect by being fixed to pulp fibers, the (meth)acrylamide-based polymer preferably has a viscosity of 3000 mPa s to 18000 mPa s, more preferably 3500 mPa s to 15000 mPa s, and further preferably 4000 mPa s to 13000 mPa s at a temperature of 25°C, as measured using a B-type viscometer.

[0082] In terms of the (meth)acrylamide-based polymer, a 1% by weight aqueous solution of the (A) component dissolved in water having a conductivity of 3 mS / cm at 25°C prepared from ion-exchange water and sodium sulfate has a maximum turbidity of 50 NTU to 1000 NTU at a pH of 3 to 9. This value means that when a 1% by weight aqueous solution of the (meth)acrylamide-based copolymer is prepared by dissolving the papermaking additive in an aqueous sodium sulfate solution having a conductivity of 3 mS / cm at 25°C, the aqueous solution has a maximum turbidity of 50 NTU to 1000 NTU at a pH of 3 to 9. If the turbidity satisfies this value, the pulp is moderately coagulated when the papermaking additive is added to a pulp slurry, and an excellent paper strength effect is exhibited. In addition, in terms of the same aspect, the turbidity is preferably 60 NTU to 800 NTU, and more preferably 80 NTU to 600 NTU.

[0083] The turbidity is the degree of turbidity, and is a value measured by using an ANALITE NEPHELOMETER 152 (manufactured by Mc Van Instruments) to measure 180-degree scattered light using infrared light of 900 nm. The measured value is a relative evaluation value with respect to a standard substance (formazine standard solution 400 NTU, manufactured by Wako Pure Chemical Industries, Ltd.).

[0084] The water (aqueous solution) used in the measurement of the turbidity is an aqueous sodium sulfate solution having a conductivity of 3 mS / cm at 25°C. The water used when preparing the aqueous sodium sulfate solution is preferably ion-exchange water. The ion-exchange water is water that has passed through an ion-exchange resin so that the conductivity is 0.2 mS / cm or less. The reason for using the aqueous sodium sulfate solution is that a large amount of sulfate ions or sodium ions are present in the white water during papermaking, and therefore by using sodium sulfate, an environment similar to that during papermaking can be formed, and the conductivity can be easily increased.

[0085] The turbidity is related to the degree of formation of a polyion complex (PIC) with the (meth) acrylamide-based polymer, and the value varies depending on the pH. The (meth) acrylamide-based polymer has anionic and cationic functional groups in the molecule, and thus forms a PIC by the pH of the solution approaching the vicinity of the isoelectric point. When the (meth) acrylamide-based polymer starts to form a PIC, turbidity is generated in the solution. Figure 1 is a graph when the distribution of turbidity becomes "single peak". The distribution of turbidity is as shown in Figure 1 As the pH is slowly increased, substantially, initially, the turbidity of the solution gradually becomes dense, and the value of the turbidity also continuously increases. Then, after reaching a maximum value, the turbidity becomes less dense, and the value of the turbidity also gradually decreases (this distribution is referred to as "single peak"; refer to Figure 1 ). In addition, sometimes if a too large PIC is formed, a precipitate is generated in the solution at a certain time point, and thus the turbidity becomes less dense, and the value of the turbidity decreases, and if the pH is further increased, the precipitate slowly disappears, and thus the turbidity again becomes dense, and the value of the turbidity also increases. Figure 2 is a graph when the distribution of turbidity becomes "double peak". In this case, as shown in Figure 2 the turbidity distribution when the pH is changed from 3 to 9 has two peaks (this distribution is referred to as "double peak"; refer to Figure 2 In the present application, in the case of double peak, as long as either of the peaks has a maximum value of 50 NTU to 1000 NTU, an excellent paper strength effect can be exerted.

[0086] The paper of the present application contains the papermaking additive, and as a method for producing the same, for example, the following can be mentioned: addition to a raw pulp slurry (hereinafter, also referred to as internal addition); spraying (jetting) to the surface of a wet paper; or coating to the surface of a raw paper, and the like. Furthermore, the papermaking additive is preferably diluted with water, and the nonvolatile content concentration thereof is adjusted to 0.1 to 2% by weight.

[0087] In the case of internal addition to a raw pulp slurry, the papermaking additive is added to a pulp slurry and papermaking is performed. The amount of use of the papermaking additive (calculated as the nonvolatile content of the (A) component) is not particularly limited, and is about 0.01 to 4% by weight with respect to the dry weight of the pulp. In addition, the kind of the pulp is not particularly limited, and for example, the following can be mentioned: hardwood pulp (bleached kraft hardwood pulp (Nippon Paper Chemical pulps include bleached kraft pulp (LBKP) and softwood pulp (needle bleached kraft pulp (NBKP)); mechanical pulps include ground pulp (GP), refined ground pulp (RGP), and thermomechanical pulp (TMP); and waste paper pulps such as waste corrugated paper. In addition to these, when adding additives to papermaking materials, pH adjusters such as aluminum sulfate, sulfuric acid, or sodium hydroxide can be added; papermaking chemicals such as sizing agents or wetting agents can be added; and fillers such as talc, clay, kaolin, titanium dioxide, and calcium carbonate can be used as fixing agents.

[0088] When spraying (spraying) onto the surface of wet paper, the papermaking additive is sprayed onto the surface of one or more layers of wet paper before pressing. The papermaking additive is diluted to a concentration of approximately 0.1% to 7% by weight before use. Furthermore, the viscosity after dilution is approximately 2 mPa·s to 50 mPa·s at a temperature of 25°C (concentration of 1.0% by weight, 25°C). Typically, the amount of the papermaking additive used (converted to non-volatile components) is 0.05% to 10% by weight relative to the total pulp (weight of non-volatile components).

[0089] When coating the surface of the base paper, papermaking additives are applied to the surface of the base paper using various known methods. Here, the papermaking additives applied to the surface of the base paper are referred to as "coating liquid". The viscosity of the coating liquid is typically 1 mPa·s to 40 mPa·s at a temperature of 50°C. The type of base paper can be uncoated paper made from wood cellulose fibers. The coating method is not particularly limited; examples include rod coating machines, doctor blade coating machines, air knife coating machines, calenders, roll coating machines, scraper coating machines, two-roll sizing presses, and rod metering. Furthermore, the coating amount (calculated in terms of non-volatile components) is also not particularly limited, and is typically 0.001 g / m³. 2 ~2g / m 2 Approximately, preferably 0.005 g / m 2 ~1g / m 2 about.

[0090] The paper of this invention can be used in various products, such as: coated paper, newspaper paper, liner, core, paper tube, printing and writing paper, form paper, plain paper copier (PPC) paper, paper cup paper, inkjet paper, thermal paper, etc.

[0091] [Example]

[0092] The present application will be described below by citing examples, but the present application is not limited to them. In addition, "parts" and "%" in the examples and comparative examples are weight basis unless otherwise specified.

[0093] The following compounds are shown in abbreviations.

[0094] AM: Acrylamide

[0095] DM: N,N-Dimethylaminoethyl methacrylate

[0096] DML: N,N-Dimethylaminoethyl methacrylate benzyl chloride

[0097] IA: Itaconic acid

[0098] SMAS: Sodium methylallyl sulfonate

[0099] DMAA: N,N-Dimethylacrylamide

[0100] APS: Ammonium persulfate

[0101] <Viscosity>

[0102] 1. (al) Component

[0103] A pasting liquid was obtained by adding ion exchange water so that the nonvolatile component concentration of the starch (al) used in the raw material was 20%, and stirring at 90°C for 1 hour. The viscosity of the pasting liquid adjusted to a temperature of 25°C was measured using a B-type viscometer (manufactured by Tokimec, Inc.).

[0104] 2. (Meth)acrylamide-based polymer

[0105] The viscosity of the (meth)acrylamide-based polymer (A) adjusted to a temperature of 25°C was measured using a B-type viscometer (manufactured by Tokimec, Inc.).

[0106] <Weight average molecular weight>

[0107] The weight average molecular weight of the (meth)acrylamide-based polymer (A) was measured by a gel permeation chromatography (GPC) method under the following measurement conditions.

[0108] Column: One guard column (PWXL) and two GMPWXLs manufactured by Tosoh Corporation

[0109] Eluent: Phosphate buffer solution (0.05 mol / L phosphoric acid (manufactured by Fuji Photo Film Co., Ltd. and Wako Pure Chemical Industries, Ltd.) + 0.13 mol / L sodium dihydrogen phosphate (manufactured by Fuji Photo Film Co., Ltd. and Wako Pure Chemical Industries, Ltd.) aqueous solution, pH about 2.5)

[0110] Flow rate: 0.8 ml / min

[0111] Temperature: 40°C

[0112] Refractive index (RI) detector: Shodex RI-101 manufactured by Showa Denko K.K.

[0113] Multi-angle light scattering (MALS) detector: DAWN HELEOS-II manufactured by Wyatt Corporation

[0114] Measurement sample: The sample was diluted with the eluent so that the concentration of the nonvolatile component of the (meth)acrylamide-based polymer (A) became 0.1% and then measured.

[0115] < Turbidity >

[0116] • Turbidity meter: ANALITE NEPHELOMETER 152 manufactured by McVan Instruments

[0117] • Infrared wavelength: 900 nm

[0118] • Standard substance: Formaldehyde standard solution (400 NTU) manufactured by Wako Pure Chemical Industries, Ltd.

[0119] • Sample concentration: 1% (concentration of the nonvolatile component of the (meth)acrylamide-based polymer (A))

[0120] • Solvent: water having a conductivity of 3 mS / cm at 25°C prepared from ion exchange water and sodium sulfate

[0121] • Sample temperature: 25°C

[0122] (Measurement method)

[0123] The turbidity value with respect to the change in pH was measured by slowly adding a 1% aqueous sodium hydroxide solution at a pH change of 0.1 each time in the case of increasing the pH, and by slowly adding a 1% aqueous sulfuric acid solution at a pH change of 0.1 each time in the case of decreasing the pH, using a stirrer to stir the 1% aqueous solution of the (meth) acrylamide-based polymer (A) diluted with the solvent at 500 rpm. When the turbidity value was unstable, waiting was performed until the turbidity value was stable, and the value at the time of stabilization was taken as the turbidity value. In the distribution (peak) of the turbidity obtained by the measurement, the maximum value was read. Further, in the case where the distribution (peak) of the turbidity became a double peak, the higher value was taken as the maximum value. The maximum value of the turbidity is shown in Table 1.

[0124] Production Example 1 (Production of Enzyme-modified Cationic Starch)

[0125] In a reaction apparatus including a stirrer, a thermometer, a reflux cooling tube, a dropping funnel, and a nitrogen gas introduction tube, 100 parts (nonvolatile component) of cationic starch (trade name: "CS-2", manufactured by Arakawa Chemical Industries, Inc.), 0.02 parts of α-amylase (trade name: "Kleistase L1", manufactured by Amano Enzyme, Inc.), and 36.6 parts of ion exchange water were added, warmed to 75°C, and stirred for 40 minutes, and then warmed to 90°C and further stirred for 1 hour, to obtain enzyme-modified cationic starch having a nonvolatile component concentration of 20% and a viscosity of 120 mPa-s (25°C).

[0126] Production Example 2 (Production of Enzyme-modified Amphoteric Starch)

[0127] In the same reaction apparatus as in Production Example 1, 100 parts (nonvolatile component) of amphoteric starch having a phosphate group (trade name: "Cato 3210", manufactured by Ingredion. Japan, Inc.), 0.02 parts of α-amylase (trade name: "Kleistase L1", manufactured by Amano Enzyme, Inc.), and 400 parts of ion exchange water were added, warmed to 75°C, and stirred for 40 minutes, and then warmed to 90°C and further stirred for 1 hour, to obtain enzyme-modified amphoteric starch having a nonvolatile component concentration of 20% and a viscosity of 1100 mPa-s (25°C). Further, the enzyme-modified amphoteric starch belongs to the starches having a phosphate group.

[0128] Example 1

[0129] In a reaction apparatus including a stirrer, a thermometer, a reflux cooling tube, a dropping funnel, a nitrogen gas introduction tube, urea-phosphoric acid esterized starch (trade name: "Ace P160", manufactured by Okino-miie Corn Starch Co., Ltd.) 50 parts (nonvolatile component), oxidized starch (trade name: "Ace A", manufactured by Okino-miie Corn Starch Co., Ltd.) 50 parts (nonvolatile component), and ion exchange water 400 parts were charged, and after oxygen in the liquid was removed by direct blowing of nitrogen gas, the temperature was raised to 80°C while stirring was performed. In a dropping funnel (1), 50% AM aqueous solution 644 parts (nonvolatile component: 322 parts), DM 40 parts, 60% DML 33.3 parts (nonvolatile component: 20 parts), IA 12 parts, SMAS 6 parts, 62.5% sulfuric acid aqueous solution 19.6 parts (nonvolatile component: 12.3 parts), and ion exchange water 245.1 parts were charged, and adjusted to pH 3.0 using sulfuric acid. In addition, in a dropping funnel (2), APS 0.8 parts and ion exchange water 180 parts were charged. Subsequently, from the dropping funnel (1) and the dropping funnel (2), the above-mentioned starch aqueous solution was dropped for 3 hours. After the dropping was completed, APS 0.8 parts and ion exchange water 10 parts were charged, and the reaction was performed until the viscosity shown in Table 2 was obtained. Dilution was performed using ion exchange water so that the nonvolatile component concentration became 25%, and a (meth)acrylamide-based polymer (A-1) was obtained. In Table 2, the viscosity (the value thereof was set to x), the weight average molecular weight, and the maximum value of the turbidity (the same hereinafter) are shown.

[0130] Examples 2 to 6, Examples 12 to 24, Comparative Examples 1 and 2

[0131] By the same method as in Example 1, using the components and amounts shown in Table 2, a (meth)acrylamide-based polymer (A-2) to (A-6), (A-12) to (A-24), (B-1) to (B-2) were obtained, respectively.

[0132] Example 7

[0133] In the same reaction apparatus as in Example 1, urea-phosphate esterified starch (trade name: "Ace P160", manufactured by Okamura Corn Starch Co., Ltd.) 75 parts (nonvolatile component), oxidized starch (trade name: "Ace A", manufactured by Okamura Corn Starch Co., Ltd.) 75 parts (nonvolatile component), and ion exchange water 586 parts were charged, and oxygen in the liquid was removed by direct blowing of nitrogen gas, and stirring was performed while being warmed to 80°C. In a dropping funnel (1), 50% AM aqueous solution 563.4 parts (nonvolatile component: 281.7 parts), DM 35 parts, 60% DML 29.2 parts (nonvolatile component: 17.5 parts), IA 10.5 parts, SMAS 5.3 parts, 62.5% sulfuric acid aqueous solution 17.1 parts (nonvolatile component: 10.7 parts), and ion exchange water 183.8 parts were charged, and pH was adjusted to 3.0 using sulfuric acid. In addition, in a dropping funnel (2), APS 0.8 parts and ion exchange water 60 parts were charged. Subsequently, from the dropping funnel (1) and the dropping funnel (2), dropping was performed into the starch aqueous solution over 3 hours. After the dropping was completed, APS 0.8 parts and ion exchange water 10 parts were charged, and reaction was performed until the viscosity shown in Table 2 was obtained. Dilution was performed using ion exchange water so that the nonvolatile component concentration became 25%, and a (meth)acrylamide-based polymer (A-7) was obtained.

[0134] Example 8

[0135] In the same reaction apparatus as in Example 1, urea-phosphate esterified starch (trade name: "Ace P160", manufactured by Okamura Corn Starch Co., Ltd.) 75 parts (nonvolatile component), oxidized starch (trade name: "Ace A", manufactured by Okamura Corn Starch Co., Ltd.) 75 parts (nonvolatile component), and ion exchange water 586 parts were charged, and oxygen in the liquid was removed by direct blowing of nitrogen gas, and stirring was performed while being warmed to 80°C. In a dropping funnel (1), 50% AM aqueous solution 563.4 parts (nonvolatile component: 281.7 parts), DM 35 parts, 60% DML 29.2 parts (nonvolatile component: 17.5 parts), IA 10.5 parts, SMAS 5.3 parts, 62.5% sulfuric acid aqueous solution 17.1 parts (nonvolatile component: 10.7 parts), and ion exchange water 183.8 parts were charged, and pH was adjusted to 3.0 using sulfuric acid. In addition, in a dropping funnel (2), APS 0.8 parts and ion exchange water 60 parts were charged. Subsequently, from the dropping funnel (1) and the dropping funnel (2), dropping was performed into the starch aqueous solution over 3 hours. After the dropping was completed, APS 0.8 parts and ion exchange water 10 parts were charged, and reaction was performed until the viscosity shown in Table 2 was obtained. Dilution was performed using ion exchange water so that the nonvolatile component concentration became 25%, and a (meth)acrylamide-based polymer (A-7) was obtained.

[0136] Example 9

[0137] In the same reaction apparatus as in Example 1, urea-phosphoric esterified starch (trade name: "Ace P160", manufactured by Okamura Cornstarch Co., Ltd.) 125 parts (nonvolatile component), oxidized starch (trade name: "Ace A", manufactured by Okamura Cornstarch Co., Ltd.) 125 parts (nonvolatile component), and ion exchange water 877 parts were put in, and oxygen in the liquid was removed by direct blowing of nitrogen gas, and stirring was performed while being warmed to 80°C. In a dropping funnel (1), 50% AM aqueous solution 402.4 parts (nonvolatile component: 201.2 parts), DM 25 parts, 60% DML 20.8 parts (nonvolatile component: 12.5 parts), IA 7.5 parts, SMAS 3.8 parts, 62.5% sulfuric acid aqueous solution 12.2 parts (nonvolatile component: 7.6 parts), and ion exchange water 153.2 parts were put in, and the pH was adjusted to 3.0 using sulfuric acid. In addition, in a dropping funnel (2), APS 0.8 parts and ion exchange water 60 parts were put in. Subsequently, from the dropping funnel (1) and the dropping funnel (2), dropping was performed into the starch aqueous solution over 3 hours. After the dropping was completed, APS 0.8 parts and ion exchange water 10 parts were charged, and the reaction was performed until the viscosity shown in Table 2 was obtained. Dilution was performed using ion exchange water so that the nonvolatile component concentration became 25%, and a (meth)acrylamide-based polymer (A-9) was obtained.

[0138] Example 10

[0139] In the same reaction apparatus as in Example 1, urea-phosphoric esterified starch (trade name: "Ace P160", manufactured by Okamura Cornstarch Co., Ltd.) 50 parts (nonvolatile component), the enzyme-modified cationic starch of Production Example 1 250 parts (nonvolatile component: 50 parts), and ion exchange water 200 parts were put in, and oxygen in the liquid was removed by direct blowing of nitrogen gas, and stirring was performed while being warmed to 80°C. Then, the same as in Example 1 was performed, and a (meth)acrylamide-based polymer (A-10) having a nonvolatile component concentration of 25.0% was obtained.

[0140] Example 11

[0141] In the same reaction apparatus as in Example 1, the enzyme-modified cationic starch of Production Example 1 250 parts (nonvolatile component: 50 parts), the enzyme-modified amphoteric starch of Production Example 2 250 parts (nonvolatile component: 50 parts), and ion exchange water 10 parts were put in, and oxygen in the liquid was removed by direct blowing of nitrogen gas, and stirring was performed while being warmed to 80°C. Then, the same as in Example 1 was performed, and a (meth)acrylamide-based polymer (A-11) having a nonvolatile component concentration of 25.0% was obtained.

[0142] Example 25

[0143] In the same reaction apparatus as in Example 1, urea-phosphoric esterified starch (trade name: "Ace P160", manufactured by Okamura Cornstarch Co., Ltd.) 50 parts (nonvolatile component), oxidized starch (trade name: "Ace A", manufactured by Okamura Cornstarch Co., Ltd.) 50 parts (nonvolatile component), and ion exchange water 367.8 parts were charged, and oxygen in the liquid was removed by direct blowing of nitrogen gas, and stirring was performed while being warmed to 80°C. In a dropping funnel (1), 50% AM aqueous solution 632.0 parts (nonvolatile component: 316 parts), DM 40 parts, 60% DML 33.3 parts (nonvolatile component: 20 parts), IA 12 parts, SMAS 12 parts, 62.5% sulfuric acid aqueous solution 19.6 parts (nonvolatile component: 12.3 parts), and ion exchange water 251.1 parts were charged, and adjusted to pH 3.0 using sulfuric acid. In addition, in a dropping funnel (2), APS 0.8 parts and ion exchange water 60 parts were charged. Subsequently, from the dropping funnel (1) and the dropping funnel (2), dropping was performed into the starch aqueous solution over 3 hours. After the dropping was completed, APS 0.8 parts and ion exchange water 10 parts were charged, and the reaction was performed until the viscosity shown in Table 2 was obtained. Dilution was performed using ion exchange water so that the nonvolatile component concentration became 32%, and a (meth)acrylamide-based polymer (A-25) was obtained.

[0144] Comparative Example 3

[0145] In the same reaction apparatus as in Example 1, the enzyme-modified amphoteric starch of Production Example 2 500 parts (nonvolatile component: 100 parts) and ion exchange water 10 parts were charged, and oxygen in the liquid was removed by direct blowing of nitrogen gas, and stirring was performed while being warmed to 80°C. Then, in the same manner as in Example 1, a (meth)acrylamide-based polymer (B-3) having a nonvolatile component concentration of 25.0% was obtained.

[0146] The (meth)acrylamide-based polymers of each of the examples and comparative examples were directly used as papermaking additives.

[0147] <Storage stability>

[0148] Each of the papermaking additives was left standing in a thermostat at 5°C (a condition in which aging of starch is easily performed) for one month. The viscosity of each of the papermaking additives after adjustment to a temperature of 25°C was measured, and the value thereof was set as Y (mPa-s), and Y / X was calculated. The smaller the value of Y / X, the better the storage stability, and the value thereof is preferably 1 to 2, and more preferably 1 to 1.7.

[0149] [Table 2]

[0150]

[0151] (a1) Component (※ The viscosity is a value obtained by measuring the starch which is gelatinized under the conditions)

[0152] • Urea-phosphorylated starch - Trade name: "Ace P160", manufactured by Prince Corn Starch Co., Ltd., viscosity 40 mPa-s (non-volatile component concentration 20%, temperature 25°C)

[0153] • Oxidized starch - Trade name: "Ace A", manufactured by Prince Corn Starch Co., Ltd., viscosity 400 mPa-s (non-volatile component concentration 20%, temperature 25°C)

[0154] • Enzyme-modified cationic starch - Refer to Production Example 1.

[0155] • Enzyme-modified amphoteric starch - Refer to Production Example 2.

[0156] <Sheet formation evaluation>

[0157] Evaluation Examples 1 to 25, Comparative Evaluation Examples 1 to 3

[0158] The papermaking additive of each example after the storage stability test (after storage for one month at 5°C) was diluted by adding ion exchange water so that the non-volatile component concentration became 1.0%. Then, the following sheet formation evaluation was performed. In addition, with respect to the papermaking additives of Comparative Examples 1 to 3, evaluation was not performed because of poor storage stability.

[0159] Waste corrugated paper was beaten using a Niagara beater, and calcium chloride was added to the pulp slurry adjusted to a Canadian Standard Freeness (C.S.F) of 350 ml, and the conductivity was adjusted to 3.0 mS / cm. After adding aluminum sulfate in an amount of 0.5% by weight of the non-volatile components of the pulp slurry, each papermaking additive was added in an amount so that the non-volatile components became 0.5% by weight of the non-volatile components of the pulp slurry. The pH of each pulp slurry was adjusted to 6.5. Dehydration was performed using a TAPPI (Technical Association of the Pulp and Paper Industry) sheet machine, and the paper was formed to a basis weight of 150 g / m 2 Pressing was performed for 2 minutes, and the paper was formed to a basis weight of 150 g / m 2Then, the paper was dried for 4 minutes at 105°C using a rotary dryer, and conditioned for 24 hours at a temperature of 23°C and a humidity of 50%, to obtain a finished paper 1. In addition, a finished paper 2 was obtained by papermaking without adding the papermaking additive and by the same method. The finished paper 1 was measured for the drainage, the texture, the burst strength, and the fixing rate by the following methods. The results are shown in Table 3.

[0160] <Drainage>

[0161] The Canadian Standard Freeness (C.S.F) was measured according to Japanese Industrial Standards (JIS) P 8121.

[0162] <Texture (Texture Variation Coefficient)>

[0163] The light (brightness) passing through the paper obtained in the above was taken into a commercially available measuring device (trade name "Personal Image Processing System Hyper-700", manufactured by OBS Corporation), and the brightness distribution was statistically analyzed, and the value thus obtained was used as the texture variation coefficient. The smaller the value of the texture variation coefficient, the better the texture.

[0164] <Burst Strength>

[0165] The burst strength (kPa-m 2 / g) was measured according to JIS P 8131, using the paper obtained in the above.

[0166] [Table 3]

[0167]

Claims

1. A papermaking additive comprising a (meth)acrylamide polymer, wherein the (meth)acrylamide polymer has starch (a1), (meth)acrylamide (a2), an amino-containing polymerizable monomer (a3), a carboxyl-containing polymerizable monomer (a4), and a sulfonic acid-containing polymerizable monomer (a5) as essential components. in, (a1) The ingredients include: starches with phosphate groups (a1-1), selected from the group consisting of urea-phosphated starch and amphoteric starches with phosphate groups; and starches (a1-2), selected from the group consisting of unmodified starch, oxidized starch and cationic starch.

2. The papermaking additive according to claim 1, wherein, The ratio of the amount of component (a1) used by weight of non-volatile components to the total amount of components (a2) to (a5) used is [(a1) / {(a2)+(a3)+(a4)+(a5)}] = 5 / 95 to 45 / 55.

3. The papermaking additive according to claim 1 or 2, wherein, When the total usage of components (a2) to (a5) is set to 100% by weight, component (a3) ​​is 1.5% to 35% by weight, component (a4) is 1% to 15% by weight, and component (a5) is 0.5% to 8% by weight.

4. The papermaking additive according to claim 1 or 2, wherein, The constituent components also include polymeric monomers (a6) having crosslinking groups.

5. The papermaking additive according to claim 1 or 2, wherein, The weight average molecular weight of (meth)acrylamide polymers is 1.5 million to 7 million.

6. The papermaking additive according to claim 1 or 2, wherein, The maximum turbidity of a 1% by weight aqueous solution of the (meth)acrylamide polymer, prepared by diluting water with a conductivity of 3 mS / cm·25℃ using water prepared by ion-exchange water and sodium sulfate, is 50 to 1000 scattering turbidity units at pH 3 to 9.

7. A method for manufacturing an additive for papermaking, comprising the method for manufacturing an additive for papermaking according to any one of claims 1 to 6, and further comprising: The step of polymerizing the constituent components, which are essential components of (a1), (a2), (a3), (a4) and (a5), in the presence of component (a1) to obtain a (meth)acrylamide polymer.

8. The method for manufacturing the papermaking additive according to claim 7, wherein, The constituent components also include polymeric monomers (a6) having crosslinking groups.

9. A paper comprising a papermaking additive according to any one of claims 1 to 6.

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