Research Progress of Paint Printing and Environmental Protection Adhesives

Pigment printing is a printing method in which pigments with no affinity and reactivity are adhered to fabrics by using a binder on the surface of the fabric. Paint printing is not limited by fabric fibers and is not affected by the weaving method. Normally, printing only requires fixing without washing, which shortens the process flow, saves energy, and reduces the pollution of printing and dyeing wastewater to the environment. The paint printing is not only used for direct printing, but also can be used for the printing effect which is difficult to obtain for dye printing according to the need for the overprint printing of similar dye discharge printing effects. Such as gold and silver powder printing, three-dimensional printing, pearl printing, extinction printing, flocking printing, simulation printing. According to statistics, global paint-printing fabrics account for more than 70% of the total output of printed fabrics. For example, in recent years, shirt printing patterns are rich and colorful. DIY (self-printing) has also become a fashion. At present, China's paint printing has made great progress, but the product structure is not yet reasonable, the majority of middle and low-end products, the profit is very meager, ordinary shirts in the international market, each piece of about US dollars, and the same blank clothing after the pattern is printed Prices can reach US dollars, and the quality and grade of paint printing products largely depend on the properties of paint printing adhesives, so the preparation of high-performance adhesives is an important direction to improve the printing technology and quality. There are also some eco-environmental problems in paint printing, such as carcinogenic aromatic amines in colorant organic pigments, formaldehyde and alkylated polyoxyethylene ether compounds (APEO) in binders, volatile organic compounds in thickeners (VOCs). )Wait. The “Infant and Young Child Clothing Standards” issued by the AQSIQ was implemented on October 1, 2008. The content of formaldehyde in textiles for infants and children shall not exceed 20mg/kg. The national mandatory standard "Definition of formaldehyde content in textiles" shall prescribe that the formaldehyde content of direct contact with skin clothing should be less than 75mg/kg, not directly in contact with skin clothing and indoor decorative textiles. The content should be less than 300mg/kg The adhesive widely used in the domestic printing industry is water-based polyacrylic acid vinegar adhesive, which has disadvantages such as hot-tempered cold brittleness, wet-friction fastness, and poor hand feel, and is difficult to use. High-grade printing products, and most of the polyacrylic acid-based paint printing binders contain a certain amount of N-methyl methacrylamide (NMA), which will release formaldehyde during baking and storage. With the enhancement of people’s awareness of environmental protection, many countries around the world, especially the European Union, have enacted many environmental laws and regulations, prompting the development of paint adhesives for the domestic market in the direction of new style, environmental protection and high performance.

1. Development of Paint Printing Adhesives The development of foreign paint printing adhesives has developed rapidly and has been rapidly updated. The current research focus is on low-temperature cross-linking adhesives. Domestically produced paint-printing adhesives are divided into three types: 1) N Once methacrylamide is used as a cross-linking monomer, the adhesive needs to be baked at a high temperature (150-170)°C, and the color fastness and washing fastness of the adhesive after cross-linked film formation can meet the requirements. 2) Adhesive made of a low-temperature cross-linking monomer such as butoxypropenylamine: 3) A binder (PUA) graft-polymerized with aqueous acrylic acrylate (PA) and polyurethane (PU). Although the latter two kinds of paint printing adhesives can meet the environmental protection requirements, but still need 80-100 °C baking in order to crosslink the adhesive film, so that the color fastness and washing fastness to achieve the corresponding requirements.

At present, the balance between handle and color fastness in paint printing, environmental protection and other issues have not been satisfactorily resolved, and the core of solving these problems is to synthesize a new environment-friendly printing adhesive, which must have the following basic features: Conjunctiva is colorless and transparent, heating is not yellowed, skin membrane is strong and elastic, adhesion is strong, washable and dry-cleaned, resistant to sunlight and aging, 2 soft, feel good, and not sticky; 3 various colors of printed fabrics The degree is not lower than the dye printing standard.

Emulsion adhesives are typically polyacrylic butadiene, butadiene, vinyl acetate (VAc). Classes and polyurethanes, where polyacrylic adhesives are the most common type of adhesive. Acrylic vinegar emulsion has the advantages of large relative molecular mass, fast dry film formation, good adhesion to various substrates, high transparency, etc. It is the main film-forming substance of high-grade latex paints, and its raw material sources are extensive. The production capacity of vinegar-based acrylic acid and general-purpose acrylic vinegar in China has reached a new level of 1,064,000 t/a and 1,100,000 t/a, respectively, and the downstream products of acrylic acid and vinegar are mostly environmentally-friendly and green products, which are in line with current trends in the world. .

1.1.1 Copolymer Copolymerization Acrylic acrylate monomers can be divided into soft monomers. The low glass transition temperature of these monomers can impart a certain degree of flexibility to the coating, so that the polymer can be used well at low temperatures. Such as acrylic vinegar (BA), acrylic acetylene (EA), 2-ethylhexyl acrylate (2-EHA); 2 hard monomer, can give the coating a higher operating temperature and a certain degree of gloss, and make the coating resistant Scratching. Such as acrylic methyl ethyl methacrylate, etc.; 3 functional monomers, there are two types of mercapto monomers and cross-linking monomers. The shuttle-based monomers such as acrylic acid, methacrylic acid, etc., can increase the stability of the adhesive emulsion, perform cross-linking catalysis, and have a self-thickening effect. Cross-linking monomers such as acrylic acid, acryl acetic acid, propylene oxide, and the like, molecular structures include methyl (-CH2-OH) and epoxy groups. Such adhesives can crosslink after baking to form a three-dimensional network structure, but they must be baked at high temperatures, wasting energy, and may also damage the substrate. With the improvement of paint printing requirements, various types of modified adhesive products have emerged, and the monomer systems for polymerization have been continuously updated.

To reduce the cost and improve the adhesive's water resistance, alkali resistance, hardness, stain resistance and anti-powdering, etc., Liu Fangfang introduced Styrene (St) to replace the commonly used methyl methacrylate, St filming temperature High, St alone) does not reduce the amount of vinyl acetate monomer and the cost of the adhesive. Vinyl acetate can reduce the cost of the adhesive, but the VAc water resistance is poor, for which VAc is used. The VAc/St/BA core-shell emulsion adhesive MFT was prepared for the core, which has good water resistance and low cost, and the application effect is equivalent to the acrylic emulsion adhesive.

Commonly used Acrylic Cool Series self-crosslinking adhesives contain methacryloylamine, a large amount of free formaldehyde, and related research personnel at home and abroad have done a lot of research on this, choosing different self-crosslinking monomers and functionalities. Monomer replaces N-methyl acrylamide to make environment-friendly formaldehyde-free printing adhesive. A new chemical crosslinking system was explored. According to different chemical mechanisms, Shen Cuihui used self-crosslinking monomer 807-3 to replace N. Once methacryloylamine was used, an environmentally friendly low-temperature paint-printing adhesive was synthesized by pre-emulsification semi-continuous emulsion polymerization with acrylic vinegar as the basic raw material. The performance of the adhesive meets the set requirements, and the amount of free formaldehyde on the printed fabric is qualified. In addition, Chen Baoguo chose to use aldehyde-free reactive monomer G and methacrylic acid as mixed cross-linking monomers. Xiao Jihua et al. developed their own reactive monomers M and N. The synthesized adhesives have reached the expected goals.

1.1.2 Copolymer modifier 1. Waterborne polyurethane. A single polyacrylic vinegar series has a low viscosity, and a thickening agent is required for the latex paint coating. The use of an adhesive for easy gelation and the poor flexibility of the formed rubber film impose limitations on its application. The water-based WPU polyurethane has the characteristics of high viscosity and good flexibility of the formed film. The modification of the PA with the WPU can combine the advantages of the two organically, thereby improving the performance of the acrylic vinegar. Deng Aimin and others modified the synthesized PA by means of physical mixing of WPU. The acrylic acid vinegar and its derivatives were the main monomers and acrylic acid was the functional monomer. The emulsion polymerization method was used to synthesize polyacrylic acid vinegar emulsion. Aqueous polyacrylamide was used to modify the polyacrylic acid vinegar emulsion. The effect of initiator, acrylic acid and waterborne polyurethane content on the properties of the emulsion and the paint film was studied at a stirring speed of 200 r/min. The results showed that at the stirring speed, the initiator, acrylic acid, and aqueous polyurethane content were 0.8% and 0.3, respectively. The stability and appearance of the emulsion obtained under the conditions of % and 40% are good, the viscosity is 88 mPa·s, the film has good flexibility, and the adhesion is first-order infrared spectrum analysis shows that the modified polyacrylic acid vinegar emulsion has polyacrylic acid vinegar and Polyurethane cool composite structure.

2. Silicone. Silicone polymer is a kind of new strong functional polymer material. It has the advantages of soft texture, luster, low surface energy, and physiological inertness. It is widely used as a soft finishing agent for fabrics. PA has poor water resistance, poor adhesion, and high temperature change. Poor, poor print feel, poor color fastness, poor air permeability and poor moisture permeability, etc. Silicone is used to modify acrylic vinegar adhesives to make silicone modified polyacrylic vinegar adhesives. Improves the softness, abrasion resistance, and corrosion resistance of paint-printing fabrics, and imparts properties such as non-fouling properties.

Silicone-modified polyacrylic acid vinegar is mainly achieved through physical blending, solution polymerization and bulk polymerization, emulsion copolymerization of core-shell emulsion polymerization, and interpenetrating network structural emulsions. Wang Xiaojuan Synthesizes silicone modified acrylic vinegar adhesive with octamethylcyclotetrasiloxane (D4), sodium dodecylbenzene sulfonate, methyl methacrylate, oxime, sodium bicarbonate, etc. . Infrared spectroscopy analysis showed that the acryl-based polymer and the silicone monomer were copolymerized. The optimal synthesis conditions were: polysiloxane (octamethylcyclotetrasiloxane) dosage 10%, m (hard monomer): m (soft monomer) = 1:5, reaction temperature 80°C, initiator amount 0.4% (for vinyl monomer quality), emulsifier usage 4% (total monomer mass), used as a coating printing binder At the same time, the finished fabric has good fastness, soft and smooth touch, and is equivalent to the hydrophilicity of the unmodified adhesive. The formaldehyde-free fabric released by the adhesive meets the requirements of environmental protection. In addition, Peng Yonggang and others used D4 and vinyl silane coupling agent for ring-opening polymerization to obtain a vinyl-containing polysiloxane emulsion, which was used in the modification of acrylic vinegar emulsion to obtain a soft and colored hand. Excellent fastness paint printing adhesive.

3. Butadiene. Acrylic Copolyurethane Coat Emulsion Coating Printing Adhesive has a good performance in foreign countries, but at present, the adhesive produced in China is basically free of butadiene, because butadiene is gaseous at room temperature, and the production technology requirements high. In view of this, Zeng Qingle and others have explored various factors affecting the emulsion copolymerization of butadiene and acrylic acid acrylates, indicating that the emulsion copolymer latexes are suitable for coating printing adhesives.

1.1.3 Improvements in Emulsifiers The presence of emulsifiers in adhesives reduces the adhesion of the adhesive to the surface of the substrate and also gives the surface properties of the adhesive, the compaction of the emulsion film, the abrasion resistance, and the water resistance. Such as causing a certain impact. In order to solve the above problems, people have tried to replace traditional emulsifiers with polymerizable emulsifiers, which can not only improve the feel of the fabric, but also improve the resistance to dry cleaning and washing. The polymerizable emulsifier has a double bond that can participate in the polymerization reaction, and can act as a copolymerization component to participate in the polymerization and binding to the molecular chain, and can also stabilize the latex particles, and can effectively prevent migration of the emulsifier after the film formation and improve the coating film. The water resistance and adhesion. Gu Xiangjun and others synthesized a styrene/acrylic acid/methacrylic acid methacrylate ternary copolymer emulsion adhesive with homemade polymerizable emulsifier maleic acid and fatty alcohol polyoxyethylene ether monosodium salt instead of traditional emulsifiers. The synthetic adhesive is used for paint printing. Zhu Wenjun and others used self-made functional and reactive emulsifiers and interpenetrating polymer network technology to synthesize a new type of NC-203 adhesive, which has good adhesion and has been used by many garment accessories companies for hot melt. After finishing the rubber, the finished fabric has good peel strength and ideal physical indicators.

In addition, soap-free emulsion polymerization does not add or add a small amount of emulsifier emulsion polymerization during the reaction to overcome the shortcomings of traditional emulsion polymerization, and soap-free emulsion particles of uniform size, clean surface, widely used in biology, medicine, chemical industry, etc. field. Shen Feiye et al. used soap-free emulsion polymerization, selected suitable cationic monomers and initiators, and synthesized a stable cationic polymer emulsion by radical polymerization. The effects of soft monomer BA, cationic monomer M, initiator APS dosage, stirring speed and other factors on the properties of the emulsion were discussed. It was used as a binder for coating dyeing, and the effect was better than that of anionic binder. The wet rubbing fastness is similar and the hand feels soft.

1.2 Polyurethane Coatings Printing Adhesives Water-soluble polyurethanes have a dry film and their molecular composition is combined with soft and hard segments. The ratio is appropriate, giving the film better softness and mechanical strength. Particles are fixed to the fiber surface. In addition, the water-soluble polyurethane contains terminal NCO, which can cross-link with an OH in the cellulose fiber. In addition, the macromolecular repeating unit contains active hydrogen, and isocyanate which can not react with the molecule itself. Cross-linking is formed to further improve the fastness of paint printing. Liu Mei and others are isophorone diisocyanate (IPDI), polyethylene glycol 1000 (PEG1000), 2,2-dimethylpropionic acid (DMPA), triethylamine (TEA), and diethylene three. Amine was used as raw material to synthesize aqueous polyurethane, which has good resistance to electrolytes, acid and alkali, and its application as a coating printing binder is based on indexes such as rubbing fastness, soaping fastness, and hand feel. Water-based polyurethane coating printing adhesive is a new type of environment-friendly adhesive. It is a binary colloid formed by dispersing polyurethane fine particles in a continuous aqueous phase. It has non-flammable, non-toxic, non-environmental pollution, and no fire. Hidden dangers and other advantages have drawn increasing attention from people.

2 Improvement of the Polymerization Method 2.1 Core-shell structure The core-shell polymerization method can improve the blocking property of the adhesive to reduce the number of printing jams and increase the printing quality. People have been working hard to develop a paint-free adhesive with a formaldehyde-free low-temperature core-shell structure, which can achieve satisfactory fabric fastness under low-temperature baking or no-baking conditions, completely solve the problem of free formaldehyde, and improve The problem of poor hand-feeling in paint printing is an environmentally friendly product. Jiang Xue et al. chose a novel cross-linking monomer instead of N-methyl methacrylamide to prepare a core-shell environmental adhesive using a semi-continuous seed emulsion polymerization method. Transmission electron microscope (TEM) observed that the binder emulsion particles had obvious nucleus. Shell structure. The analysis results showed that the solid content of the binder emulsion was about 30%, the particle size distribution was uniform, the particle size was about 150 nm, and the particle size gradually became larger with the increase of the amount of cross-linking monomer. The use of acrylic light polypropylene cross-linking monomer has a high reactivity and is easy to form a gel. Its use for cotton fabric coating printing has good rubbing fastness, scrubbing fastness, soaping fastness and feel.

2.2 Interpenetrating network (IPN) structure IPN can change the performance of polymers to a great extent, and the preparation method is not complicated. The additives in the printing and dyeing industry are prepared into IPN to meet the process requirements, and the product quality can be improved. Color fastness and feel. Qing Zhengan et al. used a microemulsion polymerization method, selected acrylic monomers and silicone-based functional monomers, and developed a paint-printing environmental protection adhesive with an interpenetrating network structure. Wu et al. proposed the use of an IPN-based polyorganosiloxane/poly(styrene-acrylic butyl vinegar) as a binder to greatly improve dyeing performance, gloss, water resistance, and toluene resistance.

2.3 Radiation Initiated Polymerization Radiation polymerization can be carried out at lower temperatures. The temperature has little effect on the polymerization rate and relative molecular mass, and there are no initiator residues in the polymerization. Yang Jianjun and other in-situ emulsion polymerization process, the use of drilling 60-r under the radiation to prepare a waterborne acrylic vinegar-polyurethane aldehyde-free paint printing adhesive AH-2A, the reaction process is easy to control, product quality is stable, storage stability, Is a new type of aldehyde-free, APEO-free green product. After the product is used by the user, it is considered that the product has good resistance to electrolytes, the printed fabric has a soft hand, and all performance indicators can meet the requirements of the paint printing process.

3 Concluding remarks The domestic and foreign textile printing and dyeing industry paint adhesives are continuously updated, mainly by improving the fastness, improving the hand feel, reducing energy consumption, and reducing pollution, in order to achieve better results, industrialization of innovation results, thereby increasing economic efficiency And social benefits, the future direction of development will focus on the following aspects: 1 reduce product costs, develop excellent performance of non-acrylic vinegar adhesive. 2. The development of cross-linking environmentally-friendly cross-linking agent at room temperature, only natural drying, truly low-carbon, and will not release free formaldehyde and APEO, in line with environmental requirements. 3. Research on new emulsion polymerization processes and initiation techniques such as IPN, soap-free emulsion polymerization, UV-bakable type, without conventional hot baking, soaping, and drying processes.