CN100526348C - High solid content vinyl acetate-ethylene copolymer emulsion and method for synthesizing the same - Google Patents

Abstract

The present invention relates to high solid content vinyl acetate-ethylene copolymer latex for binder and the synthetic method, including 55 to 75 portion of vinyl acetate, 24 to 45 portion of ethylene, 3 to 5 portion of N-methylol acrylamide, 2 to 4 portion of PVA1788 and PVA0588, 0.4 to 1.0 portion of the compound of nonionic emulsifying agent nonyl phenol polyoxyethylene alkyl ether and anion emulsifying agent alkyl sulphate with 2:1 mixture ratio, 0.2 to 1.0 portion of 35 percents oxydol with 1:1 mixture ratio, 0.05 to 0.4 portion of formol zinc sulphate, 0.1 to 0.5 portion of ferrous sulphate, 0.5 to 1.0 portion of regular dodeca-carbon thiol-alcohol, 0.05 to 0.35 portion of potassium phosphate, 0.1 to 0.5 portion of sodium bicarbonate and 45 to 55 portion of de-ionized water. With the adoption of latex polymerization, low-residual monomer VAE latex with solid content more than 65 percents is synthesized, which is used as binder to be applied in timber processing industry and packaging industry.

Description

A kind of vinyl acetate-ethylene copolymer emulsion with solid content greater than 65% and its synthesis method

Technical field:

The invention relates to a vinyl acetate-ethylene copolymer emulsion (abbreviation: VAE emulsion) with a solid content greater than 65% for adhesives and a synthesis method, especially for wood and packaging adhesives with a high solid content greater than 65%. VAE emulsion.

Background technique:

VAE emulsion is a binary or multi-component copolymerized polymer emulsion synthesized by emulsion polymerization with vinyl acetate and ethylene as the main monomers. Generally, the content of vinyl acetate is 70-90%, and the content of ethylene is 14-16%. Since the ethylene segment acts as an internal plasticizer in the copolymer, the glass transition temperature and film-forming temperature of the VAE emulsion are reduced, which endows the VAE emulsion with many advantages, that is, good low-temperature performance, not easy to be brittle, high bonding strength, and not easy to crack. Degumming occurs, fast bonding, no pollution, etc. VAE emulsion has good compatibility with many additives, which can reduce costs, and its composite materials have high cost performance. Therefore, VAE emulsions are widely used in construction, coatings, adhesives, packaging, textiles, wood processing and other industries. Vinyl acetate-ethylene copolymer emulsion was first obtained by the American H.F.Mark in 1928 by the low-pressure method. In 1938, ICI Corporation published a patent for VAE emulsion high-pressure polymerization, with a pressure of 21MPa and a temperature of 85°C. The Du Pont Company of the United States realized industrialization in 1960. In 1965, the Air Products & Chemical Company of the United States developed VAE emulsion industrial products by medium-pressure polymerization (5-15MPa), which are mainly used for adhesives. In 1967, Bayer Company of Germany published the method of free radical copolymerization in solution. In the 1970s, VAE emulsions developed rapidly and their properties continued to improve. The research on the components affecting the emulsion polymerization system (such as initiators, emulsifiers and protective colloids, etc.) was mainly carried out. Polyvinyl alcohol was used as the protective colloid system. , the prepared VAE emulsion has excellent viscosity, fast curing speed, strong adhesion to PVC film, but poor water resistance, and cannot be shared with borax and dextrin. With the protective colloid system combined with non-ionic surfactant and carboxymethyl cellulose, the prepared VAE emulsion has excellent adhesion to PVC and good water resistance, but poor wet viscosity and slow curing speed. In the late 1980s, due to the copolymerization of unsaturated carboxylic acid or carboxylic acid ester monomers, the performance of VAE emulsions could also be improved. Gradually began to study VAE emulsion ternary copolymerization, and introduced functional monomers such as acrylate, acrylamide, maleic anhydride, and unsaturated dicarboxylic acid during the polymerization process. In the past ten years, the gradual maturity of polymerization technologies such as seed emulsion polymerization and microemulsion polymerization has provided a new research direction for VAE emulsions to improve the curing speed and bond strength in the application field. Foreign countries mainly develop VAE emulsions with high solid content and high cost performance, and VAE emulsion products with a solid content as high as 60-65% have appeared. At present, the preparation of foreign VAE emulsion usually adopts medium-pressure emulsion polymerization process, the polymerization reaction pressure is 1.5-5.0MPa, and the polymerization reaction temperature is 40-70°C. The mass fraction of ethylene is generally 14-18%, and there are mainly two synthetic processes: batch method and continuous method. The continuous method adopts on-line measurement and conversion rate control technology. The product quality is stable and the production capacity is high, but the conversion rate is low and the residual monomer content is high. The advantages of the batch method are that the process flow is simple, the variety switching is convenient, the polymerization conversion rate is high, and the residual monomer content is low. U.S.Pat.No.6,673,862 uses polyvinyl alcohol and polyoxyethylene nonionic surfactant to form a composite surfactant, uses hydrogen peroxide-ferrous sulfate as a redox initiation system, and synthesizes vinyl acetate by free radical emulsion polymerization A VAE emulsion with a content of 50-95% (based on 100 parts of monomer, the same below), an ethylene content of 5-50%, and a solid content of 65-75%. There are also U.S. Pat. No. 4,921,898, U.S. Pat. No. 5,070,134, U.S. Pat. No. 5,110,856 and U.S. Pat. No. 5,629,370 and so on. U.S.Pat.No. 6,756,438 uses vinyl carbonate, ethylene and vinyl acetate as reactive monomers to synthesize a vinyl copolymer emulsion in two steps. Related reports also include U.S.Pat.No.6,593,412, U.S.Pat.No.2,511,942, U.S.Pat.No.5,567,527, WO 99/62970, etc. U.S. Pat. No. 4,263,418 grafts functional monomers such as acrylic acid (or methacrylic acid) and vinyl aromatic hydrocarbons to vinyl prepolymers to achieve the adhesive properties of modified vinyl copolymer emulsions. U.S.3,347,811 dissolves the EVA resin with an ethylene content of more than 50% in an organic solvent, and adds it into water containing an emulsifier under high-speed stirring to form an emulsion, and then evaporates the solvent. Although this method avoids the equipment difficulties caused by high pressure, it consumes toxic solvents and a large amount of energy, which increases the cost, so there is no industrialization report.

my country's VAE emulsion development, application research lags behind foreign countries. At present, there are mainly two sets of VAE emulsion production devices in my country, namely Beijing Organic Chemical Plant and Sichuan Vinylon Plant, which were respectively introduced from Reichold Company of the United States in the late 1980s, with an annual output of 10,000 tons. The production capacity reaches 32,000 tons/year and 37,000 tons/year respectively. The difference is that the raw material ethylene of the Beijing Organic Chemical Plant is obtained by cracking petroleum, while the raw material ethylene of the Sichuan Vinylon Plant is obtained by dehydrating ethanol in the presence of a catalyst. At present, the main domestic products are general-purpose products, and there is no high-solid content VAE emulsion synthesis industrial production technology and products. Chinese patent CN1306015A adopts a graft copolymerization process route and introduces a preparation method of vinyl acetate-ethylene latex with high ethylene content. The method is to dissolve solid EVA resin with an ethylene content of 60% into vinyl acetate monomer, add it into water containing emulsifier, colloid stabilizer, and buffer under high-speed stirring, stir and emulsify at a high speed at 70-80°C, and then Transfer to an autoclave, feed ethylene monomer to a pressure of 2.5-4.0MPa, add an aqueous initiator solution, carry out emulsion polymerization at 70±5°C, and continuously add the aqueous initiator solution to obtain VAE latex with an ethylene content of 24%. Chinese patent CN99121796.9 proposes a method for dissolving solid EVA resin in vinyl acetate-acrylate monomer compounds (rather than dissolving in organic solvents), and performing emulsion polymerization under high-speed stirring to obtain a - Latex with shell structure, core is EVA, its ethylene has long sequence structure, suitable for soil coagulant.

Invention content:

The object of the present invention is to take hydrogen peroxide-ferrous sulfate as initiator, take vinyl acetate, ethylene, N-methylolacrylamide three monomers as comonomers, adopt emulsion polymerization mechanism, synthesize low Residual monomer VAE emulsion, used as adhesive in wood processing industry and packaging industry.

VAE emulsion can be used for the bonding of PVC decorative film to laminated board, particle board, hard fiberboard or fiberboard; the bonding of fireproof veneer to laminated board, particleboard, hard fiberboard or fiberboard; etc.) bonding of veneers to particleboard, hardboard or fibreboard. Adding a small amount of additives to the VAE emulsion can make a laminating adhesive with excellent performance, which is widely used in the packaging of paper-plastic composite products, mainly for polyvinyl chloride film, oriented polypropylene film, polyolefin film and color printing Compounding of paper, kraft paper, etc.

The technology adopted in the present invention:

1) The present invention adopts the intermittent high-temperature emulsion polymerization technology in which monomers and various additives are continuously added in batches, and the initiator is continuously added, and a composite emulsification system composed of anionic emulsifier and nonionic emulsifier is adopted; the initiation system adopts oxidation-reduction system. The temperature control is a two-stage step temperature control, and the temperature control range is 50°C-90°C. Adopt external circulation to remove reaction heat temperature control technology.

2) Synthetic component distribution ratio: by mass

Monomer: 55-75 parts of vinyl acetate, 25-45 parts of ethylene and 3-5 parts of N-methylolacrylamide;

Protective colloid: 2-4 parts, polyvinyl alcohol 1788 and polyvinyl alcohol 0588, the ratio is 2:1;

Emulsifier: 0.4-1.0 parts, non-ionic emulsifier nonylphenol polyoxyethylene alkyl ether and anionic emulsifier alkyl sulfate compound, the ratio is 1:1;

Initiation system: 0.2-1.0 parts of 35% hydrogen peroxide, 0.05-0.4 parts of zinc formaldehyde sulfoxylate and 0.1-0.5 parts of ferrous sulfate;

Molecular weight regulator: 0.5-1.0 parts of n-dodecyl mercaptan;

Electrolyte: 0.05-0.35 parts of potassium phosphate;

pH regulator: 0.1-0.5 parts of sodium bicarbonate;

Deionized water: 45-55 parts.

3) Process:

1. Preparation of raw materials

1) Preparation of surfactant:

Add deionized water, protective colloid, emulsifier, n-dodecyl mercaptan, ferrous sulfate, zinc formaldehyde sulfoxylate and potassium phosphate into the surfactant tank, stir at room temperature for 15-20min, then heat up to 80- 90°C, fully dissolved and mixed for later use;

2) Preparation of initiator solution:

Add deionized water and 35% hydrogen peroxide into the initiator tank, stir for 15 minutes, and prepare a 1.5-2.5% initiator solution for later use;

3) Preparation of pH regulator

Add deionized water and sodium bicarbonate into the pH adjuster tank, stir well and set aside;

1. Feed production

Pump the prepared surfactant into the reaction vessel, start the circulation pump, add some monomer vinyl acetate and N-methylol acrylamide for pre-emulsification, and at the same time add ethylene to boost the pressure to the set pressure of 3.85MPa, and pass through the circulating water Control the temperature of the reaction system at 70-75°C, and then gradually add the initiator solution to make the material start to undergo emulsion polymerization reaction under the oxidation-reduction system. After the initiator solution is added, the reaction temperature will gradually rise. At this time, the monomer is continuously added. For vinyl acetate, the reaction temperature is controlled at 75-80°C by adjusting the addition rate of the initiator solution, and ethylene is continuously added to control the reaction pressure at 9.0-10.0MPa with ethylene. A large amount of heat generated by the reaction is taken away by circulating water. After the addition, gradually stop the addition of ethylene. When the addition of the initiator solution increases significantly and the reaction temperature continues to drop, it enters the finishing period. At this time, add an excessive amount of initiator and raise the temperature to 85-95°C to reduce the residual Monomer content, after 20 minutes, the reaction is over, adding a pH regulator, degassing, mixing, filtering, and cooling to obtain the product.

Effect of the present invention

(1) Replace low-temperature polymerization with high-temperature polymerization to reduce energy consumption. In high-temperature polymerization, in addition to heating the materials from normal temperature to polymerization reaction temperature at the initial stage of reaction, the maintenance and increase of reaction temperature can be supplemented by polymerization reaction heat; while low-temperature polymerization Not only does it consume energy to lower the material from normal temperature to the polymerization reaction temperature (such as 5°C), but it also consumes energy to remove a large amount of polymerization heat during the reaction process.

(2) Improve the conversion rate of the polymerization reaction, reduce the amount of recovered monomers, the conversion rate rises from 95% to 97%, and the residual vinyl acetate content is less than 0.8%, which not only reduces energy consumption, but also greatly reduces the chance of causing pollution.

(3) adopt monomer and initiator to add technology continuously, step by step, not only can improve conversion rate, and make monomer chain-extend evenly; Good compatibility, the prepared adhesive has excellent fluidity, water retention, cohesiveness and mechanical stability under high shear conditions.

(4) The ethylene content of this product is 23-25%, the minimum film forming temperature is lower than -14°C, the film is softer after film forming, and has excellent low temperature resistance.

(5) The present invention adopts the process of removing the heat of reaction by stepwise heating and external circulation, so that the reaction temperature is controlled stably, the production cycle is long, and the product filter residue is less.

(6) The product has a high solid content of over 65%, stable storage, and a wide range of uses. It is suitable for fast bonding and special bonding, with high initial adhesion and fast curing speed.

Detailed ways

Example 1:

1. Preparation of raw materials

1) Preparation of surfactant

Add 35 parts of deionized water, 3 parts of protective colloid, 0.6 part of emulsifier, 0.3 part of ferrous sulfate, 0.2 part of zinc formaldehyde sulfoxylate, 0.2 part of potassium phosphate, and 1.0 part of n-dodecyl mercaptan in the surfactant tank , stirred at room temperature for 15-20min, then heated up to 80-90°C, fully dissolved and mixed for later use.

2) Preparation of initiator solution

Add 10 parts of deionized water and 0.5 part of 35% hydrogen peroxide into the initiator tank, stir for 15 minutes, and prepare a 1.5-2.5% initiator solution for later use.

3) Preparation of pH regulator

Add 8 parts of deionized water and 0.2 part of sodium bicarbonate into the pH regulator tank, stir well and set aside.

2. Feed production

Pump the prepared surfactant into the reaction vessel, start the circulation pump, add 42 parts of the initial monomer vinyl acetate and 3 parts of N-methylolacrylamide for pre-emulsification, and add ethylene at the same time to raise the pressure to the set pressure of 3.85 MPa. The temperature of the reaction system is controlled at 70-75° C. by circulating water, and then the initiator solution is gradually added to make the material start to undergo emulsion polymerization under the oxidation-reduction system. After the initiator solution is added, the reaction temperature will gradually rise. At this time, 28 parts of monomer vinyl acetate are continuously added, and the reaction temperature is controlled at 75-80 ° C by adjusting the addition speed of the initiator solution. A total of 30 parts of ethylene are continuously added. Use ethylene to control the reaction pressure at 9.0-10.0MPa, and the large amount of heat generated by the reaction will be taken away by the circulating water. After the continuous addition of vinyl acetate, gradually stop the ethylene feeding. Finishing period, at this time, add excess initiator and increase the temperature to 85-95°C to reduce the residual monomer content, after 20 minutes the reaction is over, add a pH regulator, degassing, mixing, filtering, cooling to obtain product.

3 Physical properties of high solid content VAE emulsion

Table 1 Performance index of high solid content VAE emulsion

Grade LHEVLac-2 Exterior White or light blue homogeneous emulsion pH value 5.3 Total solids content (%) 65.2 Viscosity (mPa.s) 3843 Glass transition temperature (°C) -15 Residual vinyl acetate (%) 0.75 Particle size (μm) 185 Ethylene content (%) 23.7

.4 Application performance: 1

Table 2 Comparison of application performance between VAE emulsion of the present invention and PVAC emulsion

project VAE emulsion PVAC emulsion Curing time (room temperature)/min 8 twenty three Elongation/% 532 310 Weight loss of film after 24h in water at 20℃/%≤ 1.8 3.3 Residual VAC content/% 0.7 Heat sealing temperature/℃ 85 Solid content/% 65.2 50.0 Particle size/μm 1.85 1.75

Example 2:

Take 55 parts of deionized water, 4 parts of protective colloid, 1.0 part of emulsifier, 0.5 part of ferrous sulfate, 0.4 part of zinc formaldehyde sulfoxylate, 0.35 part of potassium phosphate, 1.0 part of 35% hydrogen peroxide, 0.5 part of sodium bicarbonate, 75 parts of vinyl acetate 5 parts, 5 parts of N-methylolacrylamide, 25 parts of ethylene, 0.5 part of n-dodecyl mercaptan, the method for preparing high-solid content VAE emulsion with the method for Example 1, the result is the same as Example 1.

Example 3:

Take 45 parts of deionized water, 4 parts of protective colloid, 0.4 part of emulsifier, 0.1 part of ferrous sulfate, 0.05 part of zinc formaldehyde sulfoxylate, 0.05 part of potassium phosphate, 0.2 part of 35% hydrogen peroxide, 0.1 part of sodium bicarbonate, 65 parts of vinyl acetate 4 parts, 4 parts of N-methylolacrylamide, 45 parts of ethylene, 0.7 part of n-dodecyl mercaptan, the method for preparing high solid content VAE emulsion with the method for Example 1, the result is the same as Example 1.

Example 4:

Take 50 parts of deionized water, 3 parts of protective colloid, 0.8 parts of emulsifier, 0.3 parts of ferrous sulfate, 0.2 parts of zinc formaldehyde sulfoxylate, 0.25 parts of potassium phosphate, 0.2 parts of 35% hydrogen peroxide, 0.1 parts of sodium bicarbonate, 60 parts of vinyl acetate 4 parts, 4 parts of N-methylolacrylamide, 40 parts of ethylene, the method for preparing high solid content VAE emulsion with embodiment 1, result is with embodiment 1.

Claims (2)

1, a kind of solid content is greater than 65% vinyl acetate-ethylene copolymer emulsion, and it is characterized in that: it is to be made up of following component by mass:

Monomer: vinyl acetate between to for plastic 55-75 part, ethene 25-45 part and N hydroxymethyl acrylamide 3-5 part;

Protective colloid: 2-4 part, be polyvinyl alcohol 1788 and polyvinyl alcohol 0588, proportioning is 2:1;

Emulsifying agent: 0.4-1.0 part, be nonionic emulsifying agent Nonyl pheno alkyl oxide and anionic emulsifier alkylsurfuric acid salt composite, proportioning is 1:1;

Initiator system: 0.1～0.5 part in 35% hydrogen peroxide 0.2-1.0 part, 0.05～0.4 part on formaldehyde sulfoxylate zinc and ferrous sulfate;

Molecular weight regulator: dodecyl mercaptan carbon 0.5-1.0 part;

Ionogen: 0.05～0.35 part of potassiumphosphate;

PH regulator agent: sodium bicarbonate 0.1-0.5 part;

Deionized water: 45～55 parts.

2, a kind of solid content is greater than the synthetic method of 65% vinyl acetate-ethylene copolymer emulsion, and it is characterized in that: component according to claim 1 follows these steps to synthesize:

(1) preparation of raw material

1) preparation of tensio-active agent:

In the tensio-active agent groove, add deionized water, add protective colloid, emulsifying agent, ferrous sulfate, formaldehyde sulfoxylate zinc, potassiumphosphate and dodecyl mercaptan carbon, stir 15-20min at normal temperatures, be warming up to 80-90 ℃ then, standby after fully dissolving, the mixing;

2) preparation of initiator solution:

Add deionized water, 35% hydrogen peroxide in the initiator groove, stir 15min, the initiator solution that is mixed with 1.5-2.5% is standby;

3) preparation of pH regulator agent

In pH regulator agent groove, add deionized water, sodium bicarbonate, standby after fully stirring;

(2) production that feeds intake

The tensio-active agent for preparing is pumped in the reaction vessel, start recycle pump, add partial monosomy vinyl acetate between to for plastic and N hydroxymethyl acrylamide and carry out pre-emulsification, add ethene simultaneously and boost to setting pressure 3.85MPa, by recirculated water control reactive system temperature is 70-75 ℃, add initiator solution then gradually, make material under oxidation-reduction system, begin to carry out emulsion polymerization, after initiator solution adds, temperature of reaction will rise gradually, add the monomer vinyl acetate between to for plastic this moment continuously, make temperature of reaction be controlled at 75-80 ℃ by the adding speed of regulating initiator solution, constantly add ethene, control reaction pressure at 9.0-10.0MPa with ethene, a large amount of heats that reaction produces are taken away by recirculated water, after vinyl acetate between to for plastic adds continuously, stop ethylene feed gradually, when the initiator solution add-on obviously increases and temperature of reaction when continuing to descend, enter Cleansing Period, at this moment, add excessive initiator and temperature is increased to 85-95 ℃ to reduce residual monomer content, afterreaction finished in 20 minutes, add the pH regulator agent, through deaeration, mix, filter, cooling promptly gets product.