阅读说明：本技术 一种微涂升华热转印纸及其制备方法 (Micro-coating sublimation thermal transfer paper and preparation method thereof ) 是由 戴贤中 王建明 童小波 高峰 李玉 张辉 于 2020-04-17 设计创作，主要内容包括：本发明涉及造纸技术领域,公开了一种微涂升华热转印纸及其制备方法,包括原纸和涂覆在原纸上的吸墨涂层,制备吸墨涂层所用的涂料以重量份记,原料包括：0.6~2份聚环氧氯丙烷-二甲胺改性的纳米二氧化硅,6~16份丙烯酰胺改性的聚乙烯醇,100~200份水,涂料的涂布量为3~5g/m<Sup>2</Sup>。本发明对涂层中的粘结剂和颜料进行改性,利用粘结剂和颜料之间的反应,将颜料和粘结剂通过化学键连接起来,避免涂层较薄时颜料从粘结剂中脱落影响对油墨的吸收量；并且改性后的粘结剂和颜料不但可以加速油墨的吸收,还可以将油墨固定在涂层内,避免油墨渗透至纸面。(The invention relates to the technical field of papermaking, and discloses micro-coating sublimation thermal transfer paper and a preparation method thereof, wherein the micro-coating sublimation thermal transfer paper comprises base paper and an ink absorption coating coated on the base paper, the coating used for preparing the ink absorption coating is recorded in parts by weight, and the raw materials comprise: 0.6-2 parts of polyepichlorohydrin-dimethylamine modified nano silicon dioxide, 6-16 parts of acrylamide modified polyvinyl alcohol and 100-200 parts of water, wherein the coating weight of the coating is 3-5 g/m 2 . The invention modifies the binder and the pigment in the coating, and utilizes the reaction between the binder and the pigment to connect the pigment and the binder through chemical bonds, thereby avoiding the influence of the falling of the pigment from the binder to the absorption capacity of the printing ink when the coating is thin; and the modified binder and the modified pigment can accelerate the absorption of the ink and fix the ink in a coating to prevent the ink from permeating into a paper surface.)

1. The micro-coating sublimation thermal transfer paper is characterized by comprising base paper and an ink absorption coating coated on the base paper, wherein the ink absorption coating is prepared from the following coating materials in parts by weight: 0.6-2 parts of polyepichlorohydrin-dimethylamine modified nano silicon dioxide, 6-16 parts of acrylamide modified polyvinyl alcohol and 100-200 parts of water, wherein the coating weight of the coating is 3-5 g/m²。

2. The micro-coated sublimation thermal transfer paper according to claim 1, wherein the coating is prepared by the following steps:

A) preparing the nanometer silicon dioxide modified by polyepichlorohydrin-dimethylamine: dispersing nano silicon dioxide in xylene, adding gamma-chloropropyltrimethoxysilane, heating at 75-85 ℃ for reaction for 8-10 h, filtering, and extracting the product in toluene for 20-30 h to obtain chloropropylated nano silicon dioxide; adding chloropropylated nano-silica into a mixed solution of polyepichlorohydrin-dimethylamine and NaOH, stirring and reacting for 3-5 h at 85-95 ℃, filtering, washing a product with methanol and water, and drying to obtain the polyepichlorohydrin-dimethylamine modified nano-silica;

B) preparation of acrylamide-modified polyvinyl alcohol: dissolving vinyl acetate, acrylamide and azobisisobutyronitrile in methanol, introducing nitrogen for 15-20 min, heating to 60-70 ℃, carrying out heat preservation reaction for 4-6 h, precipitating with water, repeatedly cleaning, filtering, and drying to obtain a copolymer; adding the copolymer into boiling methanol, stirring for dissolving, cooling to 25-35 ℃, adding a methanol solution of sodium hydroxide, stirring for reacting for 15-20 min, heating to 50-55 ℃, keeping the temperature for reacting for 15-20 min, standing, filtering, repeatedly washing a product with methanol, and drying to obtain the acrylamide modified polyvinyl alcohol;

C) preparing a coating: dissolving acrylamide modified polyvinyl alcohol in water at 85-95 ℃ in proportion, adding polyepichlorohydrin-dimethylamine modified nano-silica, stirring and reacting for 3-5 h, and cooling to obtain the coating.

3. The micro-coated sublimation thermal transfer paper as claimed in claim 2, wherein the mass-volume ratio of the nano silica to the gamma-chloropropyltrimethoxysilane in the step A) is 1 g: (1-2 mL); the mass fraction of polyepichlorohydrin-dimethylamine in the mixed solution is 10-15%, the mass fraction of sodium hydroxide is 4-6%, and the mass volume ratio of the added chloropropylated filler to the mixed solution is 1 g: (20-30 mL).

4. The micro-coated sublimation thermal transfer printing paper according to claim 2 or 3, wherein the nano silica has a particle size of 50 to 100 nm.

5. The micro-coated sublimation thermal transfer printing paper according to claim 2, wherein the molar ratio of vinyl acetate to acrylamide in preparing the copolymer in the step B) is (30-40): 1, the mass of the azodiisobutyronitrile is 0.07-0.09% of the total mass of the vinyl acetate and the acrylamide, and the volume ratio of the vinyl acetate to the methanol is 1: (30-50); the mass-to-volume ratio of the copolymer to methanol in the subsequent step was 1 g: (50-100 mL), and the sodium hydroxide in the methanol solution of the added sodium hydroxide accounts for 3-5% of the mass of the copolymer.

6. The micro-coated sublimation thermal transfer paper as claimed in claim 1, wherein the base paper has a basis weight of 80-110 g/m²The size for preparing the base paper comprises 20-40% of bleaching agent by massWhite natural color softwood pulp and 60-80% bleached hardwood pulp with pulp size of 30-40%^oSR, wet weight 2.5-4.5 g.

7. The micro-coated sublimation heat transfer printing paper according to claim 6, wherein 150 to 200kg of pulp internal filler, 0.5 to 1.0kg of degassing agent, 15 to 20kg of wet strength agent, 5 to 10kg of pulp internal glue and 20 to 30kg of AKD are added into the pulp; the inner pulp filler is light calcium carbonate, the wet strength agent is a PPE wet strength agent with the solid content of 12-15%, the inner pulp glue is cationic starch, and AKD is alkyl ketene dimer.

8. A method for preparing the micro-coated sublimation thermal transfer printing paper as claimed in any one of claims 1 to 7, characterized by comprising the following steps:

(1) preparing pulp of base paper after pulping, and adding pulp internal filler, wet strength agent, pulp internal glue, AKD and degassing agent into the pulp according to a proportion;

(2) making the pulp on a net to obtain base paper;

(3) squeezing and pre-drying the base paper;

(4) surface sizing is carried out on the base paper after the drying;

(5) sizing and drying the base paper;

(6) coating the front surface of the base paper after sizing and drying by using a coating;

(7) and the coated paper sheet firstly enters a non-contact hot air drying box for pre-drying, then enters a post-drying part for final drying, and is subjected to press polishing to obtain the micro-coating sublimation thermal transfer paper.

9. The preparation method of the micro-coated sublimation heat transfer paper as claimed in claim 8, wherein the sizing solution used in the step (4) comprises styrene-containing copolymer surface sizing agent and weak cation surface sizing tapioca starch in a mass ratio of 1 (40-70), the solid content of the sizing solution is 8-12%, and the sizing amount is 1.5-3 g/m²。

10. The method for preparing the micro-coated sublimation heat transfer paper according to claim 8, wherein the concentration of the upper web during papermaking in the step (2) is 0.3-0.8%; the moisture content of the base paper dried before in the step (3) is 4-7%, and the moisture content of the paper sheet dried finally in the step (7) is 3-5%.

Technical Field

The invention relates to the technical field of papermaking, in particular to micro-coating sublimation heat transfer paper and a preparation method thereof.

Background

The sublimation heat transfer printing technology is a method for transferring patterns to printing materials such as fabrics and the like by printing the patterns on heat transfer printing paper by adopting printing modes such as ink-jet printing, offset printing, silk-screen printing and the like, then attaching one surface of the heat transfer printing paper with the patterns to a printing stock, and changing ink on the paper into gas state to be combined with the printing stock by utilizing a hot pressing mode.

The thermal transfer paper used in sublimation thermal transfer printing mainly comprises base paper and a coating coated on the base paper, wherein the coating comprises a high molecular material binder such as polyvinyl alcohol or sodium carboxymethyl cellulose and an ink-absorbing pigment such as silicon dioxide, and the pigment is fixed on the surface of the base paper through the binder so as to improve the ink absorption of the paper and the roughness of the paper surface, thereby improving the thermal transfer printing performance of the paper. For example, the "production method of lightly coated digital thermal transfer paper" disclosed in the chinese patent literature, publication No. CN106758536B, includes preparation of internal sizing solution, preparation of surface coating solution, size disintegration, beating-size mixing process, web forming, surface sizing, and coating steps; the coating glue solution contains silicon dioxide and sodium carboxymethyl cellulose with the weight ratio of 1: 1-4.

However, in the thermal transfer paper in the prior art, if the surface coating is too thin, the ink is easy to penetrate through the coating and penetrate into the paper surface in a large amount, and the pigment content is low and is easy to fall off from the binder, so that the absorption amount of the coating to the ink is low, and the definition and the transfer quality of a transfer pattern are influenced; the thick coating can lead a large amount of pigment to be coated in the binder, so that the absorption speed of pigment particles to ink is reduced, the drying rate of the ink is reduced, the ink piling phenomenon is easy to generate, and the transfer printing precision is influenced.

Disclosure of Invention

The invention aims to overcome the defects that in the prior art, if the surface coating is too thin, ink easily permeates through the coating and permeates into the paper surface in a large amount, and meanwhile, the coating has low absorption capacity to the ink, thereby influencing the definition and transfer printing quality of a transfer printing pattern; the thick coating layer can lead most of the pigment to be coated in the binder, so that the absorption speed of the pigment particles to the ink is reduced, the drying speed of the ink is reduced, the ink piling phenomenon is easy to generate, and the transfer printing precision is influenced; the binder and the pigment in the coating are modified, and the pigment and the binder are connected through chemical bonds by utilizing the reaction between the binder and the pigment, so that the influence of the falling of the pigment from the binder on the absorption capacity of the ink when the coating is thin is avoided; and the modified binder and the modified pigment can accelerate the absorption of the ink and fix the ink in a coating to prevent the ink from permeating into a paper surface.

In order to achieve the purpose, the invention adopts the following technical scheme:

the utility model provides a scribble sublimation heat transfer paper a little, includes body paper and the blotting coating of coating on the body paper, the used coating of preparation blotting coating is with parts by weight note, and the raw materials include: 0.6-2 parts of polyepichlorohydrin-dimethylamine modified nano silicon dioxide, 6-16 parts of acrylamide modified polyvinyl alcohol and 100-200 parts of water, wherein the coating weight of the coating is3～5g/m²。

According to the invention, the surface of the nanometer silica pigment is modified by the polyepichlorohydrin-dimethylamine, so that the surface free energy of the nanometer silica can be reduced, the dispersibility and dispersion stability of the nanometer silica in the coating can be improved, the nanometer silica agglomeration in the coating can be avoided, and the ink absorption performance of the coating can be reduced. According to the invention, after acrylamide is used for modifying polyvinyl alcohol, an amide group is introduced into the polyvinyl alcohol, so that the polarity of the polyvinyl alcohol is increased, and the hydrogen bond bonding capability of the polyvinyl alcohol and the printing ink is improved, therefore, the absorption rate of the polyvinyl alcohol to the printing ink can be effectively improved, the binder and the ink absorption pigment in the coating have good absorption effect on the printing ink, the drying rate of the printing ink is further improved, and the phenomenon of ink piling is avoided, so that the transfer printing precision is not influenced.

Meanwhile, after the pigment and the binder are mixed, the terminal chlorine on the polyepichlorohydrin-dimethylamine in the modified nano-silica can generate substitution reaction with the amine of acrylamide in the modified polyvinyl alcohol, so that the nano-silica is connected with the polyvinyl alcohol through chemical bonds, the binding force of pigment particles and the binder matrix is effectively improved, and the phenomenon that the pigment particles fall off from the surface of a coating when the coating is thin and the ink absorption capacity of the coating is influenced, thereby the transfer printing quality is influenced is avoided. And the polyepichlorohydrin-dimethylamine has positive charges, and most of dye molecules in the common ink contain anionic groups and are negatively charged, so that the adsorption of the ink can be accelerated as well as the adsorption of the acrylamide, and after the reaction and the connection of the polyepichlorohydrin-dimethylamine, staggered ink blocking nets can be formed in the coating, and the ink can be adsorbed on the blocking nets after being absorbed by the coating, so that the resistance of the longitudinal diffusion of the ink is increased, and the ink is prevented from permeating the surface of a paper sheet along a polyvinyl alcohol matrix to influence the transfer effect.

Therefore, the thermal transfer paper can be realized at 3-5 g/m²Under the condition of small coating weight, the coating has good absorption capacity and absorption rate to the ink, the ink cannot permeate into paper, the ink is dried quickly, the phenomenon of ink piling is not easy to occur, and the transfer printing effect of the pattern is good.

Preferably, the preparation method of the coating comprises the following steps:

A) preparing the nanometer silicon dioxide modified by polyepichlorohydrin-dimethylamine: dispersing nano silicon dioxide in xylene, adding gamma-chloropropyltrimethoxysilane, heating at 75-85 ℃ for reaction for 8-10 h, filtering, and extracting the product in toluene for 20-30 h to obtain chloropropylated nano silicon dioxide; adding chloropropylated nano-silica into a mixed solution of polyepichlorohydrin-dimethylamine and NaOH, stirring and reacting for 3-5 h at 85-95 ℃, filtering, washing a product with methanol and water, and drying to obtain the polyepichlorohydrin-dimethylamine modified nano-silica;

B) preparation of acrylamide-modified polyvinyl alcohol: dissolving vinyl acetate, acrylamide and azobisisobutyronitrile in methanol, introducing nitrogen for 15-20 min, heating to 60-70 ℃, carrying out heat preservation reaction for 4-6 h, precipitating with water, repeatedly cleaning, filtering, and drying to obtain a copolymer; adding the copolymer into boiling methanol, stirring for dissolving, cooling to 25-35 ℃, adding a methanol solution of sodium hydroxide, stirring for reacting for 15-20 min, heating to 50-55 ℃, keeping the temperature for reacting for 15-20 min, standing, filtering, repeatedly washing a product with methanol, and drying to obtain the acrylamide modified polyvinyl alcohol;

C) preparing a coating: dissolving acrylamide modified polyvinyl alcohol in water at 85-95 ℃ in proportion, adding polyepichlorohydrin-dimethylamine modified nano-silica, stirring and reacting for 3-5 h, and cooling to obtain the coating.

In the step A), a silane coupling agent gamma-chloropropyl trimethoxy silane is firstly utilized to react with hydroxyl on the nano silicon dioxide, and chloropropyl is introduced on the surface of the nano silicon dioxide; and then, the chloropropyl group reacts with the amino group on the polyepichlorohydrin-dimethylamine to graft the polyepichlorohydrin-dimethylamine on the surface of the pigment, so as to obtain the polyepichlorohydrin-dimethylamine modified nano-silica. In the step B), vinyl acetate and acrylamide are copolymerized under the action of an initiator azobisisobutyronitrile to obtain a copolymer, and then the copolymer is saponified to obtain acrylamide modified polyvinyl alcohol. And then mixing the modified nano-silica and the modified polyvinyl alcohol in the step C) to ensure that the terminal group chlorine on the polyepichlorohydrin-dimethylamine and the amine of the acrylamide are subjected to substitution reaction, so that the nano-silica and the polyvinyl alcohol are connected through chemical bonds to obtain the coating capable of improving the transfer printing performance of the coating.

Preferably, the mass-to-volume ratio of the nano silicon dioxide to the gamma-chloropropyltrimethoxysilane in the step A) is 1 g: (1-2 mL); the mass fraction of polyepichlorohydrin-dimethylamine in the mixed solution is 10-15%, the mass fraction of sodium hydroxide is 4-6%, and the mass volume ratio of the added chloropropylated filler to the mixed solution is 1 g: (20-30 mL).

Preferably, the particle size of the nano silicon dioxide is 50 to 100 nm.

Preferably, when the copolymer is prepared in the step B), the molar ratio of the vinyl acetate to the acrylamide is (30-40): 1, the mass of the azodiisobutyronitrile is 0.07-0.09% of the total mass of the vinyl acetate and the acrylamide, and the volume ratio of the vinyl acetate to the methanol is 1: (30-50); the mass-to-volume ratio of the copolymer to methanol in the subsequent step was 1 g: (50-100 mL), and the sodium hydroxide in the methanol solution of the added sodium hydroxide accounts for 3-5% of the mass of the copolymer.

Preferably, the base paper has a basis weight of 80 to 110g/m²The pulp for preparing the base paper comprises 20-40% of bleached natural color softwood pulp and 60-80% of bleached hardwood pulp by mass fraction, the pulp size is 30-40 oSR, and the wet weight is 2.5-4.5 g.

Preferably, 150-200 kg of pulp internal filler, 0.5-1.0 kg of degasifier, 15-20 kg of wet strength agent, 5-10 kg of pulp internal glue and 20-30 kg of AKD are added into the pulp; the inner pulp filler is light calcium carbonate, the wet strength agent is a PPE wet strength agent with the solid content of 12-15%, the inner pulp glue is cationic starch, and AKD is alkyl ketene dimer.

The invention also provides a preparation method of the micro-coating sublimation heat transfer paper, which comprises the following steps:

(1) preparing pulp of base paper after pulping, and adding pulp internal filler, wet strength agent, pulp internal glue, AKD and degassing agent into the pulp according to a proportion;

(2) making the pulp on a net to obtain base paper;

(3) squeezing and pre-drying the base paper;

(4) surface sizing is carried out on the base paper after the drying;

(5) sizing and drying the base paper;

(6) coating the front surface of the base paper after sizing and drying by using a coating;

(7) and the coated paper sheet firstly enters a non-contact hot air drying box for pre-drying, then enters a post-drying part for final drying, and is subjected to press polishing to obtain the micro-coating sublimation thermal transfer paper.

Preferably, the sizing solution used in the surface sizing in the step (4) comprises a styrene-containing copolymer surface sizing agent and a weak cation surface sizing tapioca starch in a mass ratio of 1 (40-70), wherein the solid content of the sizing solution is 8-12%, and the sizing amount is 1.5-3 g/m²。

Preferably, the concentration of the top wire is 0.3-0.8% during the papermaking in the step (2); and (4) the moisture of the paper sheet finally dried in the step (7) is 3-5%.

The surface sizing is carried out on the base paper after the base paper is dried, and the coating is carried out after the base paper is sized and dried, so that the printing ink is further prevented from permeating into paper sheets, and the transfer printing effect is ensured.

Therefore, the invention has the following beneficial effects:

(1) the acrylamide is used for modifying polyvinyl alcohol, so that the absorption performance of the adhesive matrix on the printing ink is improved, and the absorption and drying of the printing ink are accelerated; the nanometer silicon dioxide is modified by polyepichlorohydrin-dimethylamine, so that the dispersibility of the nanometer silicon dioxide is improved, the pigment particles can be ensured not to be agglomerated in the coating under the condition of not adding a dispersing agent, and the ink absorption performance of the coating is ensured;

(2) after the pigment and the binder are mixed, the terminal chlorine on the polyepichlorohydrin-dimethylamine in the modified nano-silica can generate substitution reaction with the amine of acrylamide in the modified polyvinyl alcohol, so that the nano-silica is connected with the polyvinyl alcohol through chemical bonds, the binding force of pigment particles and the binder matrix is effectively improved, and the pigment particles are prevented from falling off from the surface of the coating when the coating is thin, the ink absorption capacity of the coating is influenced, and the transfer printing quality is influenced;

(3) after the polyepichlorohydrin-dimethylamine is reacted and connected with acrylamide, a staggered ink blocking net can be formed in the coating, and the ink can be adsorbed on the blocking net after being absorbed by the coating, so that the resistance of longitudinal diffusion of the ink is increased, and the ink is prevented from permeating the surface of a paper sheet along a polyvinyl alcohol matrix to influence the transfer effect.

Detailed Description

The invention is further described with reference to specific embodiments. The starting materials used in the examples of the present invention are, if not exclusively, commercially available starting materials.