Paper strength enhancer, paper

Abstract

The present invention relates to a paper strengthening agent and a paper that includes the paper strengthening agent, the paper strengthening agent including a mixture of: a (meth)acrylamide polymer (A) that has as essential constituents a (meth)acrylamide (a1), a polymerizable monomer (a2) having an amino group, and a polymerizable monomer (a3) having a carboxy group; and a metal inorganic acid salt (B) having a divalent or trivalent metal atom and a molecular weight of 30-80. The paper strengthening agent exhibits an excellent strengthening effect when used in paper.

Description

Technical Field

[0001] The present invention relates to a paper strength enhancer and paper.

Background Art

[0002] A paper strength enhancer is a chemical used to increase the strength of paper itself. Particularly in the paper industry, with the progress of closed-loop papermaking systems (such as recycling of waste paper pulp), the strength of the obtained paper is more likely to decrease due to the reduction in the strength of pulp fibers as raw materials, and the importance of paper strength enhancers is increasing.

[0003] By the way, as paper strength enhancers, (meth)acrylamide-based polymers are widely used and are classified into anionic type, cationic type, and amphoteric type according to their ionic properties. Among these, the mainstream amphoteric type (meth)acrylamide-based polymer is obtained by copolymerizing acrylamide with polymerizable monomers such as cationic monomers and anionic monomers (Patent Document 1).

[0004] When adding the polymer to the pulp slurry in the papermaking system, aluminum sulfate is added as a fixing agent before or after adding the polymer. However, with the closed-loop of the papermaking system, the fixing effect of aluminum sulfate decreases, and there is also a trend in paper mills to reduce the amount of aluminum sulfate added from the perspective of environmental load, which makes it more difficult to fully exhibit the paper strength effect of the paper strength enhancer itself, posing a problem. As a solution, a method of adding a paper strength enhancer obtained by premixing a (meth)acrylamide-based polymer and a water-soluble aluminum compound such as aluminum sulfate to the pulp slurry has been known (Patent Documents 2 and 3). Although such a mixed paper strength enhancer has merits in reducing the amount of aluminum sulfate added to the pulp slurry and enhancing the paper strength effect, its effect has been insufficient.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

[0006] The object of the present invention is to provide a paper strength enhancer that has excellent paper strength effects. [Means for solving the problem]

[0007] Through diligent research, the inventors have discovered that the aforementioned problems can be solved by incorporating a specific metal inorganic salt into a (meth)acrylamide polymer, and have completed the present invention. That is, the present invention relates to the following paper strength enhancer and paper.

[0008] 1. A paper strength enhancer comprising a mixture of a (meth)acrylamide polymer (A) having (meth)acrylamide (a1), a polymerizable monomer having an amino group (a2), and a polymerizable monomer having a carboxyl group (a3) ​​as essential components, and a metal inorganic salt (B) having a divalent or trivalent metal atom with an atomic weight of 30 to 80.

[0009] 2. The paper strength enhancer according to paragraph 1, wherein the viscosity of the mixture (at 25°C) when it is an aqueous solution (pH=6) containing 1% by weight of component (A) in terms of nonvolatile content is 5 mPa·s or more and 5000 mPa·s or less.

[0010] 3. The paper strength enhancer according to item 1 or 2 above, wherein the constituent components further comprise a polymerizable monomer having a sulfonic acid group (a4) and / or a polymerizable monomer having a crosslinking group (a5).

[0011] 4. The paper strength enhancer described in paragraph 1 or 2 above, wherein component (B) is one or more selected from the group consisting of titanium chloride, titanium sulfate, titanium phosphate, iron nitrate, iron chloride, polyferrous chloride, iron sulfate, polyferrous sulfate, iron phosphate, polyferrous phosphate, iron silicate, and polyferrous silica.

[0012] 5. The paper strength enhancer according to item 1 or 2, wherein the mixture further comprises a water-soluble aluminum compound (C).

[0013] 6. Paper containing the paper strength enhancer described in item 1 or 2 above. [Effects of the Invention]

[0014] The paper strength enhancer of the present invention exhibits excellent paper strength when used in paper. [Modes for carrying out the invention]

[0015] The paper strength enhancer of the present invention comprises a mixture of a (meth)acrylamide polymer (A) (hereinafter referred to as component (A)) having (meth)acrylamide (a1) (hereinafter referred to as component (a1)), a polymerizable monomer having an amino group (a2) (hereinafter referred to as component (a2)), and a polymerizable monomer having a carboxyl group (a3) ​​(hereinafter referred to as component (a3)) as essential components, and a metal inorganic salt (B) (hereinafter referred to as component (B)) having a divalent or trivalent metal atom with an atomic weight of 30 to 80.

[0016] (a1) The components are methacrylamide and acrylamide. These may be used individually or in combination.

[0017] (a1) The molar ratio of component is preferably 50 to 99.45 mol%, more preferably 61 to 98.88 mol%, and even more preferably 68 to 97.48 mol%, with the total constituent components being 100 mol%.

[0018] (a2) component is a polymerizable monomer having an amino group. Examples of the (a2) component include polymerizable monomers having a primary amino group, polymerizable monomers having a secondary amino group, polymerizable monomers having a tertiary amino group, and quaternized salts of these polymerizable monomers. These may be used alone or in combination of two or more.

[0019] Examples of the polymerizable monomer having a primary amino group include vinylamine, allylamine, etc. These may be used alone or in combination of two or more.

[0020] Examples of the polymerizable monomer having a secondary amino group include diallylamine, etc. These may be used alone or in combination of two or more.

[0021] Examples of the polymerizable monomer having a tertiary amino group include (meth)acrylates having a tertiary amino group such as N,N-dimethylaminoethyl (meth)acrylate, N,N-diethylaminoethyl (meth)acrylate; (meth)acrylamides having a tertiary amino group such as N,N-dimethylaminopropyl (meth)acrylamide, N,N-diethylaminopropyl (meth)acrylamide, etc. These may be used alone or in combination of two or more.

[0022] The quaternized salts of these monomers mean those obtained by reacting the polymerizable monomer having a primary amino group, the polymerizable monomer having a secondary amino group or the polymerizable monomer having a tertiary amino group with a quaternizing agent, etc. Examples of the quaternized salt may be inorganic acid salts such as hydrochloride, sulfate, or organic acid salts such as acetate. Examples of the quaternizing agent include methyl chloride, benzyl chloride, dimethyl sulfate, epichlorohydrin, etc. These may be used alone or in combination of two or more.

[0023] Among these components (a2), it is preferable to include a (meth)acrylate having a tertiary amino group and / or a quaternary salt of said (meth)acrylate. Note that "(meth)acrylate" means methacrylate or acrylate (the same applies hereinafter).

[0024] (a2) The molar ratio of component is preferably 0.5 to 20 mol%, more preferably 1 to 18 mol%, and even more preferably 2 to 16 mol%, with the total constituent components being 100 mol%.

[0025] Component (a3) ​​is a polymerizable monomer having a carboxyl group. Examples of component (a3) ​​include (meth)acrylic acid, acrylic anhydride, 2-(meth)acrylamide-N-glycolic acid, N-(meth)acryloylglycine, 3-(meth)acrylamidepropanoic acid, 4-(meth)acrylamidebutanoic acid, itaconic acid, itaconic anhydride, fumaric acid, maleic acid, and maleic anhydride. These components (a3) ​​may also be used as salts of alkali metal salts such as sodium and potassium; ammonium salts such as ammonia; or organic amine salts such as trimethylamine, triethylamine, trimethanolamine, and triethanolamine. These may be used individually or in combination of two or more. Among these, (meth)acrylic acid, acrylic anhydride, 2-(meth)acrylamide-N-glycolic acid, and itaconic acid are preferred.

[0026] (a3) The molar ratio of component is preferably 0.05 to 20 mol%, more preferably 0.1 to 15 mol%, and even more preferably 0.5 to 12 mol%, with the total constituent components being 100 mol%.

[0027] The aforementioned components may further include a polymerizable monomer (a4) having a sulfonic acid group (hereinafter also referred to as component (a4)).

[0028] Component (a4) is a polymerizable monomer having a sulfonic acid group. Examples of component (a4) include vinyl sulfonic acid, methallyl sulfonic acid, and p-styrene sulfonic acid. These components (a4) may also be used as alkali metal salts such as sodium and potassium, or as salts such as ammonium salts. These may be used individually or in combination of two or more.

[0029] (a4) The molar ratio of the component is preferably 5 mol% or less, more preferably 0.01 to 3 mol%, and even more preferably 0.01 to 2 mol%, with the total constituent components being 100 mol%.

[0030] The aforementioned components may further include a polymerizable monomer (a5) having a crosslinking group (hereinafter also referred to as component (a5)).

[0031] (a5) Examples of components include N-alkyl(meth)acrylamides such as N-methyl(meth)acrylamide, N-ethyl(meth)acrylamide, N-isopropyl(meth)acrylamide, and Nt-butyl(meth)acrylamide; N,N-dialkyl(meth)acrylamides such as N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, and N,N-diisopropyl(meth)acrylamide; N,N'-alkylenebis(meth)acrylamides such as N,N'-methylenebis(meth)acrylamide and N,N'-ethylenebis(meth)acrylamide; crosslinkable monomers having a trialyl group such as triallyl isocyanurate, triallyl trimellitate, triallylamine, and triallyl(meth)acrylamide; and triazines having a (meth)acryloyl group such as 1,3,5-triacryloyl-1,3,5-triazine and 1,3,5-triacryloylhexahydro-1,3,5-triazine. These can be used individually or in combination of two or more. In particular, the inclusion of N,N-dimethyl(meth)acrylamide and N,N'-methylenebis(meth)acrylamide is preferred.

[0032] (a5) The molar ratio of component is preferably 5 mol% or less, more preferably 0.01 to 3 mol%, and even more preferably 0.01 to 2 mol%, with the total constituent components being 100 mol%.

[0033] The aforementioned constituent components may further include monomer (a6) other than components (a1) to (a5) (hereinafter referred to as component (a6)).

[0034] Examples of component (a6) include polymerizable monomers having aromatic rings such as styrene, α-methylstyrene, and vinyltoluene; alkyl(meth)acrylates such as methyl(meth)acrylate, ethyl(meth)acrylate, n-propyl(meth)acrylate, n-butyl(meth)acrylate, 2-ethylhexyl(meth)acrylate, and cyclohexyl(meth)acrylate; vinyl carboxylates such as vinyl acetate and vinyl propionate; nitriles such as acrylonitrile; mercaptans such as 2-mercaptoethanol and n-dodecylmercaptan; alcohols such as ethanol, isopropyl alcohol, and n-pentyl alcohol; aromatic compounds such as α-methylstyrene dimer, ethylbenzene, isopropylbenzene, and cumene; and carbon tetrachloride. These may be used individually or in combination of two or more. Furthermore, the molar ratio of component (a6) is preferably 10 mol% or less, more preferably 8 mol% or less, and even more preferably 5 mol% or less, with the total constituent components being 100 mol%.

[0035] In the production of (meth)acrylamide polymers, organic acids such as acetic acid, propionic acid, butanoic acid, citric acid, succinic acid, oxalic acid, glycolic acid, and glyoxylic acid; inorganic acids such as hydrochloric acid, sulfuric acid, and phosphoric acid; inorganic salts not belonging to component (B) described below, such as sodium sulfate, potassium sulfate, and ammonium sulfate; inorganic bases such as sodium hydroxide, potassium hydroxide, and calcium hydroxide; starches such as oxidized starch, phosphate-esterified starch, urea-phosphate-esterified starch, etherified starch, cross-linked starch, APS-modified starch, enzyme-modified starch, cationized starch, and amphoteric starch; and additives such as polyvinyl alcohol, urea, defoamers, antioxidants, preservatives, and disinfectants may be added. These may be added individually or in combination of two or more, and their content is preferably 10 parts by weight or less, and more preferably 5 parts by weight or less, per 100 parts by weight of the total constituent components.

[0036] The (meth)acrylamide polymer of the present invention can be obtained by appropriately adjusting the amounts of components (a1) to (a6) used.

[0037] (Meth)acrylamide polymers are obtained by polymerizing components (a1), (a2), and (a3) ​​as essential components, and optionally components (a4), (a5), (a6), and the aforementioned additives in a solvent in the presence of a polymerization initiator.

[0038] Examples of the polymerization methods mentioned above include methods using only dropwise polymerization, methods using only simultaneous polymerization (where the monomer mixture is added all at once), and methods combining simultaneous polymerization and dropwise polymerization.

[0039] Droplet polymerization is a method of adding a monomer mixture dropwise to a reaction system that has been pre-filled with a solvent such as water. Examples of methods that use only this polymerization method include the following (1) to (3). The dropwise addition can be done continuously, or it can be stopped midway, polymerization can be allowed to proceed for a certain period of time, and then the dropwise addition can be resumed. (1) A method of dropping a monomer mixture containing all monomer components. (2) A method of preparing two or more monomer mixtures separately and then adding them dropwise simultaneously. (3) A method in which two or more monomer mixtures are prepared separately and then added dropwise in sequence.

[0040] Furthermore, examples of methods that combine simultaneous polymerization and dropwise polymerization include the following (4) to (7). (4) A method in which each monomer mixture is polymerized separately and simultaneously, and then each polymer is mixed. (5) A method in which one or more monomer mixtures are polymerized simultaneously, and then the remaining monomer mixture is added dropwise. (6) A method of polymerization in which one or more monomer mixtures are being polymerized simultaneously, and the remaining monomer mixture is added dropwise during the polymerization process. (7) A method of simultaneous polymerization by dropwise polymerization of one or more monomer mixtures, followed by the addition of the remaining monomer mixtures all at once.

[0041] Examples of solvents include water and organic solvents, which may be used individually or in combination of two or more. Examples of water include tap water, pure water, ultrapure water, deionized water, and industrial water. Examples of organic solvents include alcohols such as methanol, ethanol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, t-butyl alcohol, isobutyl alcohol, n-hexyl alcohol, n-octyl alcohol, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, and diacetone alcohol; and ethers such as ethylene glycol monobutyl ether, propylene glycol monomethyl ether, and propylene glycol monoethyl ether. The solvent content is adjusted to a polymerization concentration of preferably 5 to 50% by weight, more preferably 10 to 35% by weight.

[0042] Examples of polymerization initiators include persulfates such as ammonium persulfate, potassium persulfate, and sodium persulfate; azo compounds such as 2,2'-azobis(2-amidinopropane) hydrochloride and 2,2'-azobis[2(2-imidazolin-2-yl)propane] hydrochloride; and hydrogen peroxide. These may be used individually or in combination of two or more. Among these, ammonium persulfate, potassium persulfate, and 2,2'-azobis(2-amidinopropane) hydrochloride are preferred because they allow solution polymerization to proceed sufficiently. Furthermore, there are no particular limitations on the method of adding the polymerization initiator, and it can be added all at once, in installments, or continuously dropwise as appropriate. The content of the polymerization initiator is also not particularly limited, and is usually about 0.001 to 5 parts by weight, preferably about 0.01 to 1 part by weight, per 100 parts by weight of all components.

[0043] Polymerization conditions include, for example, a reaction temperature of typically 50-100°C (preferably 60-90°C), and a reaction time of, for example, typically 1-10 hours (preferably 1-6 hours).

[0044] The physical properties of the obtained component (A) include, for example, a weight-average molecular weight of 1 million to 10 million, preferably 1.5 million to 7 million, because the paper strength enhancer tends to exhibit superior paper strength effects. Here, "weight-average molecular weight" refers to the value obtained by gel permeation chromatography (GPC).

[0045] Furthermore, the viscosity of component (A) is typically 1,000 to 20,000 mPa·s, preferably 3,000 to 15,000 mPa·s. Here, "viscosity" refers to the value measured with a Type B viscometer in a solution with a solid content concentration of 20% by weight, pre-adjusted to a temperature of 25°C.

[0046] Furthermore, one type of component (A) may be used, or two or more different types of component (A) manufactured separately may be used in combination.

[0047] Furthermore, in the present invention, a (meth)acrylamide polymer (A') (hereinafter referred to as component (A')) that does not belong to component (A) may also be used in combination. Component (A') means a polymer that does not contain component (a2) and / or component (a3) ​​as constituent components.

[0048] Component (B) is a metal inorganic salt having divalent or trivalent metal atoms with atomic weights of 30 to 80. When component (B) is incorporated, it chemically interacts with component (A), increasing the viscosity of the resulting paper strength enhancer, and paper with superior paper strength can be obtained.

[0049] Examples of the aforementioned metal atoms include calcium, scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, and gallium.

[0050] In addition, examples of inorganic salts include nitrates, hydrogen chlorides (hydrochlorides), polyhydrochlorides (polyhydrochlorides), sulfates, polysulfates, phosphates, polyphosphates, silicates (silica salts), and polysilicates (polysilica salts).

[0051] As for component (B), any combination of the aforementioned metal atom and inorganic salt can be freely used. In addition, hydrates of component (B) may also be used. Furthermore, these components (B) may be used individually or in combination of two or more. Among these, titanium inorganic salts and iron inorganic salts are preferred because they chemically interact with component (A) and tend to have excellent paper strength effects, and one or more selected from the group consisting of titanium chloride, titanium sulfate, titanium phosphate, iron nitrate, iron chloride, polyferrous chloride, iron sulfate, polyferrous sulfate, iron phosphate, polyferrous silicate, and polyferrous silica are more preferred.

[0052] (B) The content of component (B) is preferably 0.01 to 50 parts by weight, more preferably 0.05 to 35 parts by weight, and even more preferably 0.1 to 20 parts by weight, based on the weight of nonvolatile content, per 100 parts by weight of component (A), given that the paper strength enhancer tends to have a superior paper strength effect. Here, nonvolatile content refers to the components remaining after removing volatile components such as water and organic solvents (the same applies hereinafter).

[0053] The paper strength enhancer of the present invention may also be a mixture containing a water-soluble aluminum compound (C) (hereinafter referred to as component (C)). Examples include aluminum sulfate, aluminum chloride, basic aluminum sulfate, basic aluminum chloride, aluminum silicate, polyaluminum chloride, and polyaluminum hydroxide. Component (C) may also be used in hydrate form. These may be used individually or in combination of two or more. Among these, aluminum sulfate, aluminum chloride, and polyaluminum chloride are preferred due to their availability.

[0054] The content of component (C) is preferably 10 parts by weight or less, more preferably 5 parts by weight or less, and even more preferably 2 parts by weight or less, based on the weight of nonvolatile content, per 100 parts by weight of component (A).

[0055] The paper strength enhancer of the present invention may further contain inorganic salts not belonging to component (B), such as sodium sulfate, potassium sulfate, and ammonium sulfate; starches such as oxidized starch, phosphate-esterified starch, urea-phosphate-esterified starch, etherified starch, cross-linked starch, APS-modified starch, enzyme-modified starch, cationized starch, and amphoteric starch; and additives such as polyvinyl alcohol, urea, defoamers, antioxidants, preservatives, and disinfectants.

[0056] The paper strength enhancer of the present invention is obtained as a mixture by stirring or mixing component (A) and component (B), and optionally component (A'), component (C), and the additives at room temperature. When preparing the mixture, the mixture may be heated or cooled as appropriate. As for the mixing method, component (A) and component (B), and optionally component (A') and component (C) may be mixed in their undiluted form, or one or more components selected from component (A) and component (B), and optionally component (A') and component (C) may be diluted with water beforehand before mixing. Furthermore, water may be added to further dilute the mixture after mixing. When using two or more different (meth)acrylamide polymers as component (A), they may be mixed together all at once, or the (meth)acrylamide polymers to be used may be mixed together beforehand (component (A') may be mixed in as needed), and then the remaining components may be added and mixed.

[0057] Examples of water include tap water, pure water, ultrapure water, ion-exchanged water, and industrial water. Furthermore, the non-volatile content concentration of each component after dilution is preferably adjusted as follows, in order to obtain a paper strength enhancer with appropriate viscosity while well dispersing each component. (A) Component: Preferably 0.1 to 10% by weight, more preferably 0.3 to 5% by weight (B) Component: Preferably 0.1 to 10% by weight, more preferably 0.3 to 5% by weight (C) Component: Preferably 0.1 to 10% by weight, more preferably 0.3 to 5% by weight

[0058] Regarding the physical properties of the obtained paper strength enhancer, the viscosity of the mixture (at 25°C) when an aqueous solution (pH=6) containing 1% by weight of component (A) in terms of non-volatile content is obtained is preferably 5 mPa·s to 5000 mPa·s, more preferably 10 mPa·s to 3000 mPa·s, and even more preferably 15 mPa·s to 2000 mPa·s, in order to obtain a paper strength enhancer that disperses each component well while having an appropriate viscosity and a high paper strength effect. Note that the viscosity here is the value measured with a B-type viscometer.

[0059] When measuring the viscosity mentioned above, inorganic acids such as hydrochloric acid, sulfuric acid, and phosphoric acid; inorganic bases such as sodium hydroxide, potassium hydroxide, and calcium hydroxide can be used as pH adjusters to adjust the pH.

[0060] The paper of the present invention contains the paper strength enhancer, and methods for producing it include, for example, adding the paper strength enhancer to a raw pulp slurry (hereinafter also referred to as internal addition), spraying it onto the surface of wet paper, or coating it onto the surface of base paper. The paper strength enhancer may be used as is at the non-volatile content concentration mentioned above, but it can also be further diluted with water to adjust the non-volatile content concentration to 0.1 to 10% by weight before use.

[0061] When adding the paper strength enhancer to the raw pulp slurry, the paper strength enhancer is added to the pulp slurry before papermaking. The amount of paper strength enhancer used (calculated based on the non-volatile content of component (A)) is approximately 0.01 to 4% by weight relative to the dry weight of the pulp. Examples of pulp types include chemical pulps such as hardwood pulp (LBKP) and softwood pulp (NBKP); mechanical pulps such as wood pulp (GP), refiner ground pulp (RGP), and thermomechanical pulp (TMP); and recycled paper pulp such as recycled corrugated cardboard. When adding the paper strength enhancer, other additives may also be added, such as fixatives such as aluminum sulfate, pH adjusters such as sulfuric acid and sodium hydroxide; papermaking chemicals such as sizing agents and wet paper strength enhancers; and fillers such as talc, clay, kaolin, titanium dioxide, and calcium carbonate.

[0062] When spraying the paper strength enhancer onto the surface of wet paper, spray the paper strength enhancer onto the surface of one or more layers of wet paper before sheeting. The paper strength enhancer should be diluted to a non-volatile content concentration of approximately 0.1 to 7% by weight. The viscosity after dilution is approximately 2 to 50 mPa·s at 25°C (non-volatile content concentration of 1.0% by weight, 25°C), and the amount used (in terms of non-volatile content) is usually 0.05 to 10% by weight relative to the total pulp (non-volatile content weight).

[0063] When coating the surface of the base paper, the paper strength enhancer is applied to the surface of the base paper by various known means. Here, the paper strength enhancer applied to the surface of the base paper is called the "coating liquid." The viscosity of the coating liquid is usually 1 to 50 mPa·s at a temperature of 50°C. As for the type of base paper, uncoated paper made from wood cellulose fibers can be used, and examples of coating methods include bar coaters, knife coaters, air knife coaters, calenders, gate roll coaters, blade coaters, 2-roll size presses, and rod metering. The application amount of the coating liquid (calculated in terms of non-volatile content) is usually 0.001 to 2 g / m². 2 The degree, preferably 0.005 to 1 g / m 2 It is to that extent.

[0064] The paper of the present invention can be used in a variety of products, such as coated paper, newsprint, liners, cores, paper tubes, printing and writing paper, form paper, PPC paper, cup paper, inkjet paper, thermal paper, and the like. [Examples]

[0065] The present invention will be described below with reference to examples, but the present invention is not limited thereto. In the examples and comparative examples, "parts" and "%" are based on weight unless otherwise specified.

[0066] The following compounds are shown by their abbreviations. AM: Acrylamide DM:N,N-dimethylaminoethyl methacrylate DML: N,N-dimethylaminoethyl methacrylate benzyl chloride BQ:N,N-dimethylaminoethyl acrylate benzyl chloride APDM: Dimethylaminopropylacrylamide IA: Itaconic acid AA: Acrylic acid AGA: 2-acrylamide-N-glycolic acid SMAS: Sodium methallyl sulfonate DMAA: N,N-dimethylacrylamide MBAA: N,N'-Methylenebisacrylamide APS: Ammonium persulfate

[0067] Manufacturing Example 1 In a reaction apparatus equipped with a stirrer, thermometer, reflux condenser, nitrogen gas inlet tube, and three dropping funnels, 276.5 parts of deionized water were added, oxygen was removed from the reaction system by passing nitrogen gas through it, and the mixture was heated to 90°C. 70.5 parts (21.3 mol%) of AM, 8.7 parts (8.0 mol%) of DM, 2.4 parts (0.40 mol%) of IA, 1.11 parts (0.15 mol%) of SMAS, 28.7 parts (62.5%) of sulfuric acid, 0.23 parts (0.05 mol%) of DMAA, 0.36 parts (0.05 mol%) of MBAA, and 218.9 parts of deionized water were charged into dropping funnel (1), and the pH was adjusted to around 3.0 with sulfuric acid (monomer mixture (I)). Next, 203.9 parts (61.4 mol%) of AM, 58.7 parts (8.0 mol%) of DM, 2.4 parts (0.40 mol%) of IA, 1.11 parts (0.15 mol%) of SMAS, 0.23 parts (0.05 mol%) of DMAA, 0.36 parts (0.05 mol%) of MBAA, and 466.6 parts of deionized water were charged into dropping funnel (2), and the pH was adjusted to around 3.0 with sulfuric acid (monomer mixture (II)). 0.6 parts of APS and 180 parts of deionized water were charged into dropping funnel (3). Then, the in-system catalyst was added dropwise from dropping funnel (3) over approximately 3 hours. In parallel, the monomer mixtures (I) and (II) from dropping funnels (1) and (2) were added dropwise in that order at a constant flow rate over approximately 3 hours. After the dropwise addition was complete, 0.4 parts of APS and 10 parts of deionized water were added and kept warm for 1 hour. Then, 580 parts of deionized water were added to obtain an aqueous solution of component (A-1) with a non-volatile content of 20.0%. The molar ratios of all monomer components are shown in Table 1, and the molar ratios of the monomer components added to each monomer mixture are shown in Table 2.

[0068] Manufacturing Examples 2-18 The compositions shown in Tables 1 and 2 were synthesized in the same manner as in Production Example 1 to obtain aqueous solutions of paper strength enhancers with a non-volatile content of 20.0%, respectively.

[0069] <Viscosity> The viscosity of component (A) of each manufacturing example, adjusted to a temperature of 25°C, was measured using a Type B viscometer (manufactured by Toki Sangyo Co., Ltd.). The results are shown in Table 2.

[0070] <Weight average molecular weight> The weight-average molecular weight of component (A) was measured by gel permeation chromatography (GPC) under the following measurement conditions. The results are shown in Table 2. Columns: Tosoh Corporation Guard Column PWXL (1) and GMPWXL (2) Eluent: Phosphate buffer (0.05 mol / L phosphoric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) + 0.13 mol / L sodium dihydrogen phosphate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) aqueous solution, pH approximately 2.5) Flow rate: 0.8ml / min Temperature: 40℃ RI detector: Shodex RI-101, manufactured by Showa Denko K.K. MALS detector: WYATT DAWN HELEOS-II Measurement sample: The sample was diluted with the above eluent so that the non-volatile content concentration of component (A) was 0.1% and then measured.

[0071] [Table 1]

[0072] [Table 2]

[0073] For each production example, component (A), as well as components (B) and (C) listed in Table 2, were mixed with deionized water to achieve a non-volatile content concentration of 2%. In Example 6, aqueous solutions of components (A-1) and (B-1) were used, to which deionized water was added to achieve a non-volatile content concentration of 4%.

[0074] Example 1 (A-1) 500 parts of a 2% aqueous solution of component (10.0 parts non-volatile content), 150 parts of a 2% aqueous solution of ferric polysulfate (product name: "Politex", manufactured by Nippon Steel Mining Co., Ltd.) (3.0 parts non-volatile content), and 350 parts of deionized water were charged and mixed at room temperature for 30 minutes to obtain a paper strength enhancer.

[0075] Examples 2-5, 7-36, Comparative Examples 1-4 By changing the components and amounts used as shown in Table 2, the same method as in Example 1 was used to obtain paper strength enhancers.

[0076] Example 6 (A-1) 250 parts of a 4% aqueous solution of component (10.0 parts non-volatile content), 500 parts of a 4% aqueous solution of ferric polysulfate (product name: "Politex", manufactured by Nippon Steel Mining Co., Ltd.) (20.0 parts non-volatile content), and 250 parts of deionized water were charged and mixed at room temperature for 30 minutes to obtain a paper strength enhancer.

[0077] <Viscosity> Sodium hydroxide aqueous solutions (non-volatile content concentrations: 10%, 5%, and 1% used in combination) were added to each paper strength enhancer, and the pH was adjusted to 6. After adjusting the temperature to 25°C, the viscosity was measured using a Type B viscometer (manufactured by Toki Sangyo Co., Ltd.). The results are shown in Table 3.

[0078] (Papermaking evaluation 1: Evaluation based on differences in paper strength enhancers) Corrugated waste paper was beaten using a Niagara-type beater, and calcium chloride was added to a pulp slurry prepared with Canadian Standard Freeness (CSF) 350 ml to adjust the electrical conductivity to 2.0 mS / cm. Aluminum sulfate was added to this slurry at a concentration of 1.0% (non-volatile content) relative to the weight of the non-volatile content of the pulp slurry, and the mixture was stirred for 30 seconds. Then, each of the above-mentioned paper strength enhancers was added at a concentration of 1.0% (non-volatile content of component A) relative to the weight of the non-volatile content of the pulp slurry. The pH of each pulp slurry was adjusted to 6.5 and evaluated. The samples were dewatered using a tappy sheet machine and weighed to 5 kg / cm³. 2 Press for 2 minutes, resulting in a basis weight of 150g / m². 2The paper was prepared in the following manner. Next, it was dried in a rotary dryer at 105°C for 4 minutes, and then conditioned for 24 hours at a temperature of 23°C and a humidity of 50% to obtain finished paper 1. The form, specific burst strength, specific tensile strength, and specific compressive strength of finished paper 1 were measured by the following method. These results are shown in Table 3.

[0079] <Electrical conductivity> The pH was measured using a pH / COND METER D-54 (manufactured by Horiba, Ltd.). <Ground Conditions (Coefficient of Change in Ground Conditions)> The light transmitted through the paper (luminance) obtained above was input into a commercially available measuring instrument (product name "Personal Image Processing System Hyper-700", manufactured by OBS Corporation), and the value obtained by statistically analyzing the luminance distribution was defined as the coefficient of variation of the ground conditions. A smaller value of the coefficient of variation of the ground conditions indicates better ground conditions. <Specific bursting strength> Using the paper obtained above, the specific burst strength (kPa·m) was calculated in accordance with JIS P 8131. 2 The measurement ( / g) was taken. <Specific Tensile Strength> Using the paper obtained above, the specific tensile strength (N·m / g) was measured in accordance with JIS P 8113. <Specific compressive strength> Using the paper obtained above, the specific compressive strength (N·m) was calculated in accordance with JIS P 8126. 2 The measurement ( / g) was taken.

[0080] [Table 3]

[0081] The symbols in Table 3 represent the following components. <(A) component> • A-1 to A-18: Acrylamide polymers from manufacturing examples 1 to 18 (compound in the same order) <(B) component> • B-1: Ferric polysulfate (product name: "Polytetsu", manufactured by Nippon Steel Mining Co., Ltd.) • B-2: Iron(III) chloride (Product name: "Ferric Chloride Solution", manufactured by Taiki Pharmaceutical Co., Ltd.) • B-3: Polysilica iron (product name: "PSI-025", manufactured by Naoji Pharmaceutical Co., Ltd.) • B-4: Titanium(IV) sulfate (n-hydrate) (manufactured by Kishida Chemical Co., Ltd.) <(C) component> • C-1: Aluminum sulfate (manufactured by Asada Chemical Co., Ltd., liquid aluminum sulfate) • C-2: Polyaluminum chloride (manufactured by Asada Chemical Co., Ltd.) <(D) component> • D-1: Zirconium sulfate (tetrahydrate) (manufactured by Kishida Chemical Co., Ltd.)

[0082] (Papermaking evaluation 2: Evaluation based on differences in the order of chemical addition) Evaluation Example 1, Comparative Evaluation Examples 1-3 Corrugated cardboard waste was beaten using a Niagara-type beater, and calcium chloride was added to a pulp slurry prepared in 350 ml of Canadian Standard Freeness (CSF) to adjust the electrical conductivity to 2.0 mS / cm. Aluminum sulfate was added to this slurry at a concentration of 1.0% (non-volatile content) relative to the weight of the non-volatile content of the pulp slurry. The slurry was then stirred after 15, 30, and 45 seconds, with the components listed in Table 4 added accordingly. The pH of each pulp slurry was adjusted to 6.5 for evaluation. The slurry was dewatered using a tappy sheet machine, and the resulting slurry was 5 kg / cm³. 2 Press for 2 minutes, resulting in a basis weight of 150g / m². 2 The paper was prepared in the following manner. Next, it was dried in a rotary dryer at 105°C for 4 minutes, and then conditioned for 24 hours at a temperature of 23°C and a humidity of 50% to obtain finished paper 2. The form, specific burst strength, specific tensile strength, and specific compressive strength of finished paper 2 were measured using the same method as described above. These results are shown in Table 4.

[0083] [Table 4] *1: Expressed as the amount used in terms of the non-volatile content of component (A-1).

[0084] The symbols shown in Table 4 represent the following components. • Example 1: Paper strength enhancer for Example 1 A-1: Acrylamide polymer from manufacturing example 1 • B-1: Ferric polysulfate (product name: "Polytetsu", manufactured by Nippon Steel Mining Co., Ltd.)

[0085] Table 4 shows that the paper strength enhancer (Example 1), which was a mixture of component (A) and component (B), exhibited a superior paper strength effect compared to when component (A) and component (B) were added separately to the pulp slurry.

Claims

1. The material comprises a (meth)acrylamide polymer (A) having (meth)acrylamide (a1), a polymerizable monomer having an amino group (a2), and a polymerizable monomer having a carboxyl group (a3) ​​as essential components, and a mixture of metal inorganic salts (B) having divalent or trivalent metal atoms with atomic weights of 30 to 80. A paper strength enhancer wherein component (B) is one or more selected from the group consisting of titanium chloride, titanium sulfate, titanium phosphate, iron nitrate, iron chloride, polyferrous chloride, iron sulfate, polyferrous sulfate, iron phosphate, polyferrous phosphate, iron silicate, and polyferrous silica.

2. The paper strength enhancer according to claim 1, wherein the viscosity of the mixture (at 25°C) when an aqueous solution (pH = 6) containing 1% by weight of component (A) in terms of nonvolatile content is obtained is 5 mPa·s or more and 5000 mPa·s or less.

3. The paper strength enhancer according to claim 1 or 2, wherein the constituent components further comprise a polymerizable monomer having a sulfonic acid group (a4) and / or a polymerizable monomer having a crosslinkable group (a5).

4. The paper strength enhancer according to claim 1 or 2, wherein the mixture further comprises a water-soluble aluminum compound (C).

5. Paper containing the paper strength enhancer according to claim 1 or 2.

Images