Low-weight copy paper and production method thereof

Abstract

The present application relates to the field of copy paper, specifically providing a low-weight copy paper and a production method thereof. The low-weight copy paper of the present invention is made of the following raw material components: a main material and a modified dry strength additive, the weight of the modified dry strength additive being 0.05-1% of the weight of the main material; the main material is composed of conifer pulp and sugarcane pulp in a weight ratio of 7.5:2.5-5.5:4.5; the modified dry strength additive is composed of 10-20% acrylamide monomer, 3-8% monofunctional cationic monomer, 1-5% monofunctional polyether monomer, 0.1-0.5% hydrophilic multifunctional monomer, 0.5-1% redox initiator and deionized water supplemented to 100%. Adding the modified dry strength additive of the present invention to the copy paper raw material can improve tensile strength, tear strength, smoothness and other properties, thereby achieving low weight.

Description

Technical Field

[0001] The present application relates to the technical field of copy paper, and more specifically, to a low-weight copy paper and a production method thereof. Background Art

[0002] Copy paper is a high-grade cultural industrial paper with high physical strength, excellent uniformity and transparency, good surface properties, delicate, flat and smooth properties. With the improvement of people's environmental awareness, saving paper has become a major trend. The current basis weight of copy paper is generally 15g / m 2 About, for example 14.8g / m 2 As the basis weight of copy paper decreases, the performance of copy paper, especially the dry strength, is affected, which affects its actual use. It is difficult to prepare low-basis-weight copy paper. Summary of the Invention

[0003] After analysis, the inventors found that the main reason for the deterioration of the dry strength of low-weight copy paper is that the existing dry strength additives (such as cationic polyacrylamide) have limitations and cannot make the fibers in the paper better, tighter, and more combined.

[0004] In order to solve the problems in the prior art where dry strength additives cannot make the fibers in paper better, tighter, and more combined, the present application provides a low-weight copy paper and a production method thereof.

[0005] This application adopts the following technical solutions:

[0006] A low-weight copy paper is made from the following raw material components: a main material and a modified dry strength additive, wherein the weight of the modified dry strength additive is 0.05-1% of the weight of the main material;

[0007] The main material is composed of coniferous pulp and sugarcane pulp in a weight ratio of 7.5:2.5-5.5:4.5; further, the main material is composed of coniferous pulp and sugarcane pulp in a weight ratio of 7:3-6:4. In the present invention, coniferous pulp is long fiber and sugarcane pulp is short fiber. Through the combination of long fiber and short fiber, and the fact that long fiber weighs more than short fiber, more interlacing effects are generated between long fiber and short fiber, which helps to improve the dry strength of copy paper.

[0008] The modified dry strength additive is prepared by the following method:

[0009] Prepare the following raw materials based on 100% by weight: 10-20% acrylamide monomer, 3-8% monofunctional cationic monomer, 1-5% monofunctional polyether monomer, 0.1-0.5% hydrophilic multifunctional monomer, 0.5-1% redox initiator, and the balance deionized water; add the acrylamide monomer, the monofunctional cationic monomer, the monofunctional polyether monomer, and the deionized water into a container, adjust the pH to 3-5, stir and mix evenly, pass nitrogen to deoxygenate, add 2 / 3 to 3 / 4 of the redox initiator by weight, heat to 40±2° C., react for 0.5-1 hour, continue to heat to 50±2° C., react for 1-2 hours, add the hydrophilic multifunctional monomer and the remaining redox initiator, and continue to react for 1-2 hours to obtain the modified dry strength additive.

[0010] In the present invention, functionality refers to the number of carbon-carbon unsaturated double bond groups capable of free radical polymerization in the molecular structure of a raw material monomer. For example, a monofunctional monomer is a raw material monomer containing only one carbon-carbon unsaturated double bond group capable of free radical polymerization, and a multifunctional monomer is a raw material monomer containing three or more carbon-carbon unsaturated double bond groups capable of free radical polymerization. In the present invention, a raw material monomer molecule containing two carbon-carbon unsaturated double bond groups capable of free radical polymerization is not considered a multifunctional monomer.

[0011] Preferably, the weight of the modified dry strength additive is 0.1-0.5% of the weight of the main material. The weight of the modified dry strength additive added can be adjusted according to the concentration of the modified dry strength additive. If the concentration of the modified dry strength additive is high, the weight added can be relatively low; if the concentration of the modified dry strength additive is low, the weight added can be relatively high.

[0012] Preferably, the monofunctional cationic monomer is selected from at least one of methacryloyloxyethyltrimethylammonium chloride, methacryloyloxyethyldimethylbenzylammonium chloride, acryloyloxyethyltrimethylammonium chloride, acryloyloxyethyldimethylbenzylammonium chloride, N,N-dimethylaminopropyl acrylamide, N,N-dimethylaminoethyl methacrylate, methacryloyloxypropyltrimethylammonium chloride, methacryloyloxypropyldimethylbenzylammonium chloride and acryloyloxypropyltrimethylammonium chloride.

[0013] Preferably, the general structural formula of the monofunctional polyether monomer is CH2=C(R 1 )COO(CH2CH2O) n (CH3CHCH3O) m R 2 , where R 1 is selected from hydrogen or methyl, R 2 Selected from hydrogen or C1-C8 alkyl, n≥5, m≥0, nm≥5.

[0014] In the present invention, the monofunctional polyether monomer is a water-soluble monomer.

[0015] More preferably, R 2 The moiety is selected from hydrogen or C1-C4 alkyl. Increasing the carbon chain of the alkyl group reduces the hydrophilicity of the polyether monomer. More preferably, n=5-50 and m=0. -CH2CH2O- (EO for short) is a hydrophilic segment, and -CH3CHCH3O- (PO for short) is a hydrophobic segment. A relatively large number of PO segments reduces the hydrophilicity of the polyether monomer.

[0016] Furthermore, when 5≤n≤10, m=0, R 2 is hydrogen or methyl; when 10<n≤20, 0≤m≤5, R 2 is hydrogen or C1-C4 alkyl; when n>20, 0≤m≤10, R 2 It is hydrogen or C1-C8 alkyl.

[0017] Preferably, the hydrophilic multifunctional monomer is a trifunctional monomer, and the general structural formula of the trifunctional monomer is [CH2=C(R 3 )COO(CH2CH2O) x CH2]3C-C2H5, where R 3 is selected from hydrogen or methyl, and x = 3 to 20. More specifically, x can be 3, 6, 9, 12, 15, etc.

[0018] More preferably, the multifunctional monomer accounts for 0.3-0.5% by weight of the modified dry strength additive raw material.

[0019] Preferably, the hydrophilic multifunctional monomer is a tetrafunctional monomer, and the structural formula of the tetrafunctional monomer is [CH2=C(R 4 )COO(CH2CH2O) y CH2]4C, where R 4 is selected from hydrogen or methyl, and y = 3 to 20. More specifically, y can be 3, 6, 9, 12, 15, etc.

[0020] More preferably, the multifunctional monomer accounts for 0.1-0.3% by weight of the modified dry strength additive raw material.

[0021] The multifunctional monomers used in this invention, with tri- or tetrafunctionality, primarily serve as branching points, resulting in a distinctly branched structure in the modified dry-strength additive. Each branched chain of the branched dry-strength additive is capable of bonding with fibers in the pulp (through electrostatic adsorption, hydrogen bonding, van der Waals forces, and surface interweaving forces), enhancing interfiber interactions.

[0022] Tetrafunctional monomers have more functionality than trifunctional monomers and are more likely to form cross-linked structures. Therefore, when using tetrafunctional monomers, in order to avoid the formation of cross-linked structures, the amount of tetrafunctional monomers used is less than that of trifunctional monomers.

[0023] Preferably, the weight ratio of the reducing initiator to the oxidizing initiator in the redox initiator is 1:3-3:1.

[0024] A method for preparing the low-weight copy paper described in any of the above embodiments comprises pulping, screening, forming, dehydrating, drying, gluing, calendering, and winding, wherein the modified dry strength additive described in any of the above embodiments is added to the pulping.

[0025] In summary, this application has the following beneficial effects:

[0026] 1. The present application designs the molecular structure of the modified dry strength additive. In addition to the existing cationic segments that can generate electrostatic adsorption with negatively charged fibers, the following two structures are added to the molecular chain: (1) A multifunctional monomer is used to form branching points, so that the modified dry strength additive of the present application is a polymer with a branched structure, and more branched structures are formed in the molecular structure. More branched structures can form better binding effects with more fibers, improve the binding force between fibers, and bind more, tighter, and stronger. (2) Monofunctional polyether monomers are used. On the one hand, the ether bonds in the polyether can generate hydrogen bonds with the hydroxyl groups and ether bonds in the fibers, thereby improving the binding force between the modified dry strength additive and the fibers. On the other hand, after the polyether segments in the polyether interact with the fibers, the steric hindrance of the polyether segments is beneficial to the dispersion and stability of the fibers, and the obtained copy paper is more uniform.

[0027] 2. The modified dry strength additive of this application is used as a fiber binding material to improve the interaction between fibers, making different fibers more numerous, stronger, and tighter, thereby improving the dry strength of copy paper. As a fiber dispersing material, it is conducive to the uniform and stable dispersion of the bound fibers, improving the surface properties of the copy paper, making it smoother, more delicate, and more lustrous. Therefore, this application can comprehensively improve the performance of copy paper by using the modified dry strength additive of the present invention, even if the basis weight is as low as 12g / m 2 , and can also have good tensile strength, tear strength, smoothness and other properties, meeting the requirements.

[0028] 3. In the preparation of the modified dry strength additive, the present application first allows acrylamide monomers, cationic monomers and polyether monomers, all of which are monofunctional, to undergo free radical polymerization to form a single straight chain with a long carbon chain, and then adds a multifunctional monomer to participate in the polymerization reaction. The inventors found that the above preparation method adopted in the present application has the following advantages: (1) By controlling the amount and order of addition of the multifunctional monomer, the multifunctional monomer is prevented from forming crosslinks, and each functional group in the multifunctional monomer can form a branched structure, thereby forming a branched structure; (2) Because long carbon chain polymer segments have already formed in the reaction system before the addition of the multifunctional monomer, the long carbon chain polymer segments form branched structures under the action of the multifunctional monomer. Therefore, the branched structures in the formed branched polymer are also longer, and each branched structure has the effect of entanglement and bonding with the fiber, which is conducive to improving the bonding effect with the fiber. DETAILED DESCRIPTION

[0029] The present invention is described in more detail below through specific examples and comparative examples. Unless otherwise specified, the parts in the following examples and comparative examples are parts by weight.

[0030] Preparation Example 1

[0031] Prepare the raw materials according to 100 parts by weight, 13.3 parts of acrylamide monomer, 5.1 parts of methacryloyloxyethyl dimethylbenzyl ammonium chloride, 3.2 parts of monofunctional polyether monomer CH2=CHCOO(CH2CH2O) 7.7 H, 0.4 parts of trifunctional monomer [CH2=C(CH3)COO(CH2CH2O)6CH2]3C-C2H5, 0.8 parts of redox initiator (ammonium persulfate and sodium bisulfite in a weight ratio of 1:1), and the balance is deionized water;

[0032] Acrylamide monomer, methacryloyloxyethyl dimethylbenzyl ammonium chloride, monofunctional polyether monomer, and deionized water were added to a container, the pH was adjusted to 3.5, and the mixture was stirred and mixed uniformly. Nitrogen was passed through the container for 20 minutes to remove oxygen. 0.55 parts of a redox initiator was added, the temperature was raised to 40±2°C, and the reaction was continued for 1 hour. The temperature was further raised to 50±2°C, and the reaction was continued for 1 hour. The trifunctional monomer and the remaining redox initiator were added, and the reaction was continued for 1.5 hours. The temperature was then lowered and the pH was adjusted to 3 to obtain a modified dry strength additive. No precipitate was present in the product.

[0033] Preparation Example 2

[0034] Prepare the raw materials according to 100 parts by weight, 18.7 parts of acrylamide monomer, 7.2 parts of acryloyloxyethyl trimethyl ammonium chloride, 4.5 parts of monofunctional polyether monomer CH2=CHCOO(CH2CH2O) 16.4 (CH3CHCH3O) 2.3CH3, 0.47 parts of trifunctional monomer [CH2=C(CH3)COO(CH2CH2O)9CH2]3C-C2H5, 1 part of redox initiator (ammonium persulfate and sodium bisulfite in a weight ratio of 1:1), and the balance is deionized water;

[0035] Acrylamide monomer, acryloyloxyethyltrimethylammonium chloride, monofunctional polyether monomer, and deionized water were added to a container, the pH was adjusted to 3.5, and the mixture was stirred and mixed uniformly. Nitrogen was passed through the container for 20 minutes to remove oxygen. 0.7 parts of a redox initiator was added, the temperature was raised to 40±2°C, and the reaction was continued for 1 hour. The temperature was further raised to 50±2°C, and the reaction was continued for 1.5 hours. The trifunctional monomer and the remaining redox initiator were added, and the reaction was continued for 1.5 hours. The temperature was then lowered and the pH was adjusted to 3 to obtain a modified dry strength additive. No precipitate was present in the product.

[0036] Preparation Example 3

[0037] Prepare the raw materials according to 100 parts by weight, 12.2 parts of acrylamide monomer, 3.4 parts of methacryloyloxyethyl trimethyl ammonium chloride, 2.5 parts of monofunctional polyether monomer CH2=CHCOO(CH2CH2O) 12.9 H, 0.15 parts of tetrafunctional monomer [CH2=C(CH3)COO(CH2CH2O) 15 CH2]4C, 0.63 parts of redox initiator (ammonium persulfate and sodium bisulfite in a weight ratio of 1.5:1), and the balance deionized water;

[0038] Acrylamide monomer, methacryloyloxyethyltrimethylammonium chloride, monofunctional polyether monomer, and deionized water were added to a container, the pH was adjusted to 3.5, and the mixture was stirred and mixed uniformly. Nitrogen was passed through the container for 20 minutes to remove oxygen. 0.45 parts of a redox initiator was added, the temperature was raised to 40±2°C, and the reaction was continued for 45 minutes. The temperature was further raised to 50±2°C and the reaction was continued for 1.2 hours. The tetrafunctional monomer and the remaining redox initiator were added, the reaction was continued for 1.5 hours, the temperature was lowered, and the pH was adjusted to 3 to obtain a modified dry strength additive. No precipitate was present in the product.

[0039] Preparation Example 4

[0040] Prepare the raw materials according to 100 parts by weight, 15.4 parts of acrylamide monomer, 5.2 parts of methacryloyloxyethyl trimethyl ammonium chloride, 3.9 parts of monofunctional polyether monomer CH2=CHCOO(CH2CH2O) 12.9 H, 0.25 parts of tetrafunctional monomer [CH2=C(CH3)COO(CH2CH2O)9CH2]4C, 0.7 parts of redox initiator (ammonium persulfate and sodium bisulfite in a weight ratio of 1.5:1), and the balance is deionized water;

[0041] Acrylamide monomer, methacryloyloxyethyltrimethylammonium chloride, monofunctional polyether monomer, and deionized water were added to a container, the pH was adjusted to 3.5, and the mixture was stirred and mixed uniformly. Nitrogen was passed through the container for 20 minutes to remove oxygen. 0.5 parts of a redox initiator was added, the temperature was raised to 40±2°C, and the reaction was continued for 1 hour. The temperature was further raised to 50±2°C, and the reaction was continued for 1 hour. The tetrafunctional monomer and the remaining redox initiator were added, and the reaction was continued for 1.2 hours. The temperature was then lowered and the pH was adjusted to 3 to obtain a modified dry strength additive. No precipitate was present in the product.

[0042] Preparation Example 5

[0043] In Preparation Example 4, the amount of the tetrafunctional monomer was adjusted from 0.25 parts to 0.18 parts, and the remaining steps remained unchanged to obtain a modified dry strength additive. No precipitate was present in the product.

[0044] Preparation Comparative Example 1

[0045] According to the raw materials and weight parts in Preparation Example 1.

[0046] Acrylamide monomer, methacryloyloxyethyl dimethylbenzyl ammonium chloride, monofunctional polyether monomer, trifunctional monomer, and deionized water were added to a container, the pH was adjusted to 3.5, and the mixture was stirred and mixed evenly. Nitrogen was passed through for 20 minutes to deoxygenate. A redox initiator was added, and the temperature was raised to 40±2°C for reaction for 1 hour. The temperature was then raised to 50±2°C for reaction for 2.5 hours. The temperature was then lowered and the pH was adjusted to 3 to obtain a modified dry strength additive. No precipitate was present in the product.

[0047] Preparation Comparative Example 2

[0048] In Preparation Example 1, the monofunctional polyether monomer was replaced with hydroxyethyl methacrylate in equal parts by weight, and the remaining steps remained unchanged to obtain a modified dry strength additive. No precipitate was present in the product.

[0049] Preparation Comparative Example 3

[0050] In Preparation Example 1, the trifunctional monomer was adjusted from 0.4 parts to 0.6 parts, and the remaining steps remained unchanged to obtain a modified dry strength additive. A small amount of precipitate was present in the product.

[0051] Since multifunctional monomers have a strong tendency to undergo self-crosslinking polymerization, if a large amount is added, they are likely to undergo self-crosslinking polymerization to form precipitates, resulting in a decrease in their effectiveness as branching points.

[0052] Preparation Comparative Example 4

[0053] The trifunctional monomer in Preparation Example 1 was adjusted to an equal weight portion of pentaerythritol triacrylate, and the remaining steps remained unchanged to obtain a modified dry strength additive. A small amount of precipitate was present in the product.

[0054] The product of this comparative example has a small amount of precipitate because pentaerythritol triacrylate is insoluble in water, resulting in poor copolymerization with water-soluble monomers and easy polymerization and / or cross-linking reaction to form precipitate.

[0055] Preparation Comparative Example 5

[0056] The trifunctional monomer in Preparation Example 1 was adjusted to polyethylene glycol dimethacrylate (the average polymerization degree of polyethylene glycol was 8.1) in equal parts by weight, and the remaining steps remained unchanged to obtain a modified dry strength additive.

[0057] Preparation Comparative Example 6

[0058] According to the raw materials in Example 1, acrylamide monomer, methacryloyloxyethyltrimethylammonium chloride, monofunctional polyether monomer, and tetrafunctional monomer were mixed, and two-thirds of deionized water was added to dissolve them to obtain a monomer solution.

[0059] The remaining one third of the deionized water is used to dissolve the redox initiator to obtain an initiator solution.

[0060] Add 50% of the monomer solution to the container, pass nitrogen to deoxygenate for 20 minutes, raise the temperature to 50±2°C, add 50% of the initiator solution dropwise, and add the remaining 50% of the monomer solution and the remaining 50% of the initiator solution dropwise at the same time. Continue the reaction for 1.5 hours, cool down, and adjust the pH to 3 to obtain a modified dry strength additive.

[0061] Example 1

[0062] The design basis weight of the copy paper is 15g / m 2 70 parts of conifer pulp and 30 parts of sugarcane pulp were taken and pulped with a pulping machine. 0.5 parts of silicone oil defoamer, 0.3 parts of mildew inhibitor, 5 parts of talcum powder, 0.1 parts of hyperdispersant, and 0.1 parts of the modified dry strength additive of Preparation Example 1 were added. The pulp was mixed, screened, formed, dehydrated, dried, glued, calendered, and rolled to obtain copy paper with a basis weight of 14.8 g / m 2 .

[0063] Example 2

[0064] In Example 1, the modified dry strength additive of Preparation Example 1 was replaced by the modified dry strength additive of Preparation Example 3 of equal weight, and the other steps remained unchanged, and the basis weight of the copy paper obtained was 14.9 g / m 2 .

[0065] Example 3

[0066] The design basis weight of the copy paper is 12g / m 2 The process steps of Example 1 were followed to prepare the copy paper with a basis weight of 12.1 g / m 2 .

[0067] Example 4

[0068] In Example 3, the modified dry strength additive of Preparation Example 1 was replaced by the modified dry strength additive of Preparation Example 2 of equal weight, and the other steps remained unchanged, and the basis weight of the copy paper obtained was 12.0 g / m 2 .

[0069] Example 5

[0070] In Example 3, the modified dry strength additive of Preparation Example 1 was replaced with the modified dry strength additive of Preparation Example 3 of equal weight, and the other steps remained unchanged, and the basis weight of the copy paper obtained was 12.1 g / m 2 .

[0071] Example 6

[0072] In Example 3, the modified dry strength additive of Preparation Example 1 was replaced with the modified dry strength additive of Preparation Example 4 in an equal weight, and the other steps remained unchanged, and the basis weight of the copy paper obtained was 11.9 g / m 2 .

[0073] Example 7

[0074] In Example 3, the modified dry strength additive of Preparation Example 1 was replaced by the modified dry strength additive of Preparation Example 5 of equal weight, and the other steps remained unchanged to obtain a copy paper with a basis weight of 12.0 g / m 2 .

[0075] Example 8

[0076] In Example 3, the modified dry strength additive of Preparation Example 1 was adjusted from 0.1 parts to 0.3 parts, and the other steps remained unchanged, and the basis weight of the copy paper obtained was 12.0 g / m 2 .

[0077] Example 9

[0078] In Example 3, the modified dry strength additive of Preparation Example 1 was adjusted from 0.1 part to 0.45 part, and the other steps remained unchanged, and the basis weight of the obtained copy paper was 12.2 g / m 2 .

[0079] Example 10

[0080] In Example 3, the modified dry strength additive of Preparation Example 1 was adjusted from 0.1 parts to 0.7 parts, and the other steps remained unchanged, and the basis weight of the obtained copy paper was 11.9 g / m 2 .

[0081] Example 11

[0082] In Example 3, the modified dry strength additive of Preparation Example 1 was adjusted from 0.1 parts to 0.06 parts, and the other steps remained unchanged, and the basis weight of the copy paper obtained was 12.1 g / m 2 .

[0083] Comparative Example 1

[0084] In Example 3, the modified dry strength additive of Preparation Example 1 was replaced by the modified dry strength additive of Preparation Comparative Example 1 in an equal weight, and the other steps remained unchanged, and the basis weight of the copy paper obtained was 12.1 g / m 2 .

[0085] Comparative Example 2

[0086] In Example 3, the modified dry strength additive of Preparation Example 1 was replaced by the modified dry strength additive of Preparation Comparative Example 2 in an equal weight, and the other steps remained unchanged, and the basis weight of the copy paper obtained was 11.8 g / m 2 .

[0087] Comparative Example 3

[0088] In Example 3, the modified dry strength additive of Preparation Example 1 was replaced by the modified dry strength additive of Preparation Comparative Example 3 in an equal weight, and the other steps remained unchanged, and the basis weight of the copy paper obtained was 12.1 g / m 2 .

[0089] Comparative Example 4

[0090] In Example 3, the modified dry strength additive of Preparation Example 1 was replaced by the modified dry strength additive of Preparation Comparative Example 4 in an equal weight, and the other steps remained unchanged, and the basis weight of the copy paper obtained was 12.2 g / m 2 .

[0091] Comparative Example 5

[0092] In Example 3, the modified dry strength additive of Preparation Example 1 was replaced by the modified dry strength additive of Preparation Comparative Example 5 in an equal weight, and the other steps remained unchanged to obtain a copy paper with a basis weight of 12.0 g / m 2 .

[0093] Comparative Example 6

[0094] In Example 3, the modified dry strength additive of Preparation Example 1 was replaced by the modified dry strength additive of Preparation Comparative Example 6 in an equal weight, and the other steps remained unchanged, and the basis weight of the copy paper obtained was 11.9 g / m 2 .

[0095] Comparative Example 7

[0096] In Example 3, the modified dry strength agent of Preparation Example 1 was replaced with an equal weight of a commercially available cationic polyacrylamide dry strength agent, and the remaining steps remained unchanged, resulting in a copy paper with a basis weight of 11.9 g / m 2 .

[0097] Performance testing

[0098] The properties of the copy papers of Examples 1-11 and Comparative Examples 1-7 are shown in Table 1.

[0099] Tightness is tested in accordance with GB / T 12914-2018;

[0100] The tear index is tested according to GB / T455-1989

[0101] Smoothness is tested according to the method of GBT 456-2002;

[0102] The light transmittance is tested according to the method of GB / T 2679.1-2020.

[0103] Table 1

[0104]

[0105]

[0106] From the data in Table 1, we can see that the copy paper of this application has a low weight (12g / m 2 ) still has good performance under low quantitative conditions, so the product performance and use can be achieved.

[0107] Comparing Example 3, Comparative Example 1 and Comparative Example 6, the preparation methods are different. The present invention adopts the method of adding the multifunctional monomer later. Compared with the method of adding the raw materials all at once or adding the raw materials in batches, the obtained modified dry strength additive has better effect.

[0108] Comparing Examples 3, 8, 9, 10 and 11, the added amounts of the modified dry strength additive are different, and the effects on the copy paper are also different. As the amount of the modified dry strength additive increases, the performance of the copy paper first improves and then decreases.

[0109] Comparing Example 3 with Comparative Example 2, the monofunctional polyether monomer contains more ether bonds than the hydrophilic hydroxyethyl methacrylate, and can form more hydrogen bonds with the ether bonds or hydroxyl groups in the fibers, so the bonding force between the fibers is also better.

[0110] Comparing Example 3 and Comparative Example 5, the use of multifunctional monomers can form more branched structures than difunctional monomers, and has a stronger effect on the fibers. Therefore, the bonding force between the fibers is also higher.

[0111] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A low-weight copy paper, characterized by: It is made of the following raw material components: a main material and a modified dry strength additive, wherein the weight of the modified dry strength additive is 0.05-1% of the weight of the main material; The main material is composed of conifer pulp and sugarcane pulp in a weight ratio of 7.5:2.5-5.5:4.5; The modified dry strength additive is prepared by the following method: Prepare the following raw materials based on 100% by weight: 10-20% acrylamide monomer, 3-8% monofunctional cationic monomer, 1-5% monofunctional polyether monomer, 0.1-0.5% hydrophilic multifunctional monomer, 0.5-1% redox initiator, and the balance is deionized water; Add the acrylamide monomer, the monofunctional cationic monomer, the monofunctional polyether monomer, and the deionized water into a container, adjust the pH to 3-5, stir and mix evenly, pass nitrogen to deoxygenate, add 2 / 3 to 3 / 4 weight of the redox initiator, heat to 40±2° C. and react for 0.5-1 hour, continue to heat to 50±2° C. and react for 1-2 hours, add the hydrophilic multifunctional monomer and the remaining redox initiator, continue to react for 1-2 hours, and obtain the modified dry strength additive; The monofunctional cationic monomer is at least one selected from the group consisting of methacryloyloxyethyltrimethylammonium chloride, methacryloyloxyethyldimethylbenzylammonium chloride, acryloyloxyethyltrimethylammonium chloride, acryloyloxyethyldimethylbenzylammonium chloride, diallyldimethylammonium chloride, N,N-dimethylaminopropylacrylamide, N,N-dimethylaminoethyl methacrylate, methacryloyloxypropyltrimethylammonium chloride, methacryloyloxypropyldimethylbenzylammonium chloride, and acryloyloxypropyltrimethylammonium chloride; The general structural formula of the monofunctional polyether monomer is CH2=C(R 1 )COO(CH2CH2O) n R 2 , where R 1 is selected from hydrogen or methyl, R 2 Selected from hydrogen or C1-C8 alkyl, n≥5; When the hydrophilic multifunctional monomer is a trifunctional monomer, the general structural formula of the trifunctional monomer is [CH2=C(R 3 )COO(CH2CH2O) x CH2]3C-C2H5, where R 3 Selected from hydrogen or methyl, x=3-20; the trifunctional monomer accounts for 0.3-0.5% by weight of the modified dry strength additive raw material; When the hydrophilic multifunctional monomer is a tetrafunctional monomer, the general structural formula of the tetrafunctional monomer is [CH2=C(R 4 )COO(CH2CH2O) y CH2]4C, where R 4 Selected from hydrogen or methyl, y=3-20; the tetrafunctional monomer accounts for 0.1-0.3% of the weight of the modified dry strength additive raw material.

2. The low-weight copy paper according to claim 1, characterized in that: The weight of the modified dry strength additive is 0.1-0.5% of the weight of the main material.

3. The low basis weight copy paper according to claim 1, characterized in that: The weight ratio of the reducing initiator to the oxidizing initiator in the redox initiator is 1:3-3:

1.

4. A method for preparing the low-weight copy paper according to any one of claims 1 to 3, comprising pulping, screening, forming, dehydrating, drying, gluing, calendering, and winding, characterized in that: Add the modified dry strength additive according to any one of claims 1 to 3 into the slurry.

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