Natural adhesives are commonly used in our lives. According to different sources, it can be divided into animal glue, vegetable glue and mineral glue. There are leather glue, bone glue, shellac, casein glue, albumin glue, fish gelatin, etc. in animal glue; starch, dextrin, rosin, gum arabic, natural rubber, etc. in plant glue; mineral wax and asphalt in mineral glue Wait. Due to its abundant sources, low price and low toxicity, it is widely used in furniture, binding, packaging and handicraft processing.

Starch adhesive

After the starch adhesive enters the 21st century, the good environmental properties of the material will become a major feature of the new material. As a non-toxic, low-cost, biodegradable and environmentally friendly natural renewable resource, starch is widely used in various industries. Especially in recent years, the world's adhesive industry production technology is developing towards energy saving, low cost, no harm, high viscosity and no solvent

As a kind of green environmental protection product, starch adhesive has attracted extensive attention and high attention in the adhesive industry. As far as the application and development of starch adhesives are concerned, the prospect of starch adhesives oxidized with corn starch is promising, and the research application is the most.

Recently, starch has been used as an adhesive mainly in paper and paper products, such as paper and carton sealing, labeling, flat topping, sticky envelopes, multi-layer paper bag bonding, and the like.

Here are some common starch adhesives:

01
Oxidized starch adhesive

A mixture of a modified starch having a low degree of polymerization containing an aldehyde group and a carboxyl group and a gelling agent prepared by heating gelatinization or room temperature gelatinization under the action of an oxidizing agent is a carrier-type starch adhesive. After oxidation, the starch forms an oxidized starch having water solubility, wettability and adhesion. The amount of oxidant is small, the degree of oxidation is not enough, the total amount of new functional groups formed by starch is reduced, the viscosity of the adhesive is increased, the initial tack is decreased, the fluidity is poorly used, and the oxidation is excessive, resulting in the viscosity of the adhesive, the initial tack, and the oxidation reaction time. It has a great influence on the acidity, transparency and hydroxyl content of the adhesive. As the reaction time prolongs, the degree of oxidation increases, and the carboxyl content increases, and the viscosity of the product gradually decreases, but the transparency is getting better and better.

02
Esterified starch adhesive

Esterified starch adhesive is a non-degradable starch adhesive. It is a new functional group of starch by esterification of hydroxyl groups of starch molecules with other substances, so that the performance of starch adhesive is improved. Because of partial cross-linking of esterified starch, The viscosity is increased, the storage stability is better, the moisture-proof and anti-toxic properties are improved, and the rubber layer can withstand high and low and alternate effects.

03
Grafted starch adhesive

The grafting of starch is to use a physical and chemical method to produce a white matrix from the starch molecular chain. When a polymer monomer is encountered, a chain reaction is formed. A starch monomer is formed on the starch backbone. Side chain. Using the characteristics of hydroxyl in polyethylene and starch molecules, hydrogen bonds can be formed between polyvinyl alcohol and starch molecules, which play a role of "grafting" between polyvinyl alcohol and starch molecules, thus making the prepared starch. Adhesive has the advantages of better adhesiveness, fluidity and anti-freezing property. Because starch adhesive is a natural polymer adhesive, it is widely researched and applied because of its low price, non-toxic and tasteless, and no pollution to the environment. Recently, starch adhesives are mainly used on paper, cotton fabric, envelopes, labels, corrugated cardboard.

04
Cellulose adhesive

Cellulose ether derivatives used as binders are mainly ethyl cellulose (EC) such as methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose: A thermoplastic, water-insoluble, nonionic cellulose alkyl ether. Good chemical stability, strong alkali resistance, excellent electrical insulation and mechanical rheology. It has the characteristics of maintaining strength and flexibility at high temperature and low temperature. It is easy to be compatible with wax, resin, plasticizer, etc., as paper, rubber, leather, Adhesive for fabrics.

Formaldehyde cellulose (CMC): ionic cellulose ether. In the textile industry, CMC is often used to replace high quality starch as a slurry for cloth. The textile is coated with CMC, which can increase the softness and improve the printing and dyeing performance. ‘In the food industry, all kinds of creamy ice cream added to CMC have good shape stability, easy coloring and softening. As an adhesive, it is used to make pens, cartons, paper bags, wallpapers and artificial wood.

Cellulose ester derivatives: mainly nitrocellulose and cellulose acetate. Nitrocellulose: also known as cellulose nitrate, the nitrogen content is generally between 10% and 14% due to the degree of esterification. The high content is commonly known as fire cotton, which was used in the manufacture of smokeless and colloidal gunpowder. The low content is commonly known as cotton wool, which is insoluble in water, but soluble in ethanol and ether mixed solvent, the solution is fire cotton glue. Because the fire cotton solvent evaporates to form a tough film, it is often used for bottle sealing, wound protection and the first plastic celluloid in manufacturing history. If an appropriate amount of alkyd resin is added as a modifier and an appropriate amount of camphor is used as a toughening agent, it becomes a nitrocellulose adhesive, which is commonly used for bonding paper, cloth, leather, glass, metal and ceramics.

Cellulose acetate: also known as cellulose acetate. The cellulose is aceticated with a mixture of acetic acid and ethanol in the presence of a sulfuric acid catalyst and then hydrolyzed with dilute acetic acid to the desired degree of esterification. Cellulose cellulose can be used to prepare solvent-based adhesives. Bonded plastics such as glasses and toys have excellent resistance to sticking and durability compared with nitrocellulose, but have poor acid resistance, moisture resistance and weather resistance.

05
Protein adhesive

Protein adhesives are a class of natural adhesives that contain protein-containing substances as the main raw material. Both animal and vegetable proteins can be used to make adhesives. According to the protein used, it is divided into animal protein (gelatin, gelatin, complex protein gel, and albumin) and plant protein (bean gum, etc.). They generally have a high degree of bondability when dry and are used in the manufacture of furniture and wood products. However, its heat resistance and water resistance are poor, and animal protein adhesives are more important.

Soy protein gel: Plant protein is not only an important food material, but also widely used in non-food fields. As far as soybean protein adhesives were concerned, as early as 1923, Johnson patented soy protein adhesives. In 1930, soy protein phenolic resin wood-based adhesive (DuPont) was weak in bonding strength and production cost was too high, and it could not be used in large quantities. In recent decades, due to the expansion of the adhesive market, the global petroleum resources are acidic and The environmental pollution problem has attracted attention, and the adhesive industry has reconsidered the new natural adhesives, which has made soybean protein adhesives a hot research topic again. Soybean adhesive is non-toxic and tasteless, easy to use, but poor in water resistance. Adding 0.1% to 1.0% by mass of a crosslinking agent such as thiourea, carbon disulfide, tricarboxymethyl sulfide, etc., can improve water resistance and obtain an adhesive for wood bonding and production of plywood.

Animal Protein Glue: Animal glue has been widely used in the furniture and wood processing industries. Commonly used products include furniture such as chairs, tables, cabinets, models, toys, sporting goods, and layerers. Newer liquid animal glues with solids content of 50%-60% include fast-curing and slow-curing types. They are bonded to the frame of the hardboard of the cabinet, movable housing assembly, difficult laminates and other hot animals that are not suitable for cheaper use. Small and medium adhesive requirements for glue.

Animal glue is a type of basic adhesive used in adhesive tapes. These tapes can be used in both common light retail bags and heavy duty tapes, such as the sealing or packaging of solid and corrugated boxes for shipping goods, where fast mechanical operations and long-lasting high bond strengths are required. At this time, the amount of bone glue is large, and the skin glue is often used alone or in combination with bone glue. According to the coating online, the adhesive used is generally formulated to have a solid content of about 50%, and can be mixed with dextrin according to 10% to 20% of the dry glue quality, and a small amount of wetting agent, plasticizer, gel inhibitor. (when necessary). The adhesive (60-63 ° C) is usually mixed with the coating on the backing paper, and the solid deposition amount is generally 25% of the paper base mass. The wet tape can be dried under tension with a steam heated roller or dried with an adjustable air direct heater.

In addition, animal glue applications include the manufacture of sandpaper and gauze abrasives, the sizing and coating of textiles and paper, and the binding of books and magazines.

06
Tannin adhesive

Tannin is an organic compound containing polyhydric phenolic groups and is widely found in the stems, skins, roots, leaves and fruits of plants. It is mainly derived from bark scraps and plants with high tannin content in wood processing. The tannin, formaldehyde and water are mixed and heated to obtain a tannin resin, and then a curing agent and a filler are added, and the tannin adhesive is obtained by stirring uniformly. Tannin adhesives have good resistance to damp heat aging. The properties of bonded wood are similar to those of phenolic adhesives. They are mainly used for the bonding of wood and the like.

07
Lignin adhesive

Lignin is one of the main components of wood, and its content is about 20-40% of wood, second only to cellulose. Lignin is difficult to extract directly from wood. The main source is pulp waste, which is extremely rich in resources. Lignin is not used alone as an adhesive, but a phenol resin-based polymer obtained by using a phenolic group of lignin and formaldehyde to function as an adhesive. In order to improve the water resistance, it can be used together with an epoxy-based isocyanate, a phenol, a resorcinol or the like. The lignin adhesive is mainly used for the bonding of plywood and particle board. However, its viscosity is high, its color is deep, and after improvement, it can be expanded.

08
Arabian tree adhesive

Acacia gum, also known as acacia gum, is an effluent glue on a wild hedgehog tree. Named for being prolific in the Arab countries. Gum arabic is mainly composed of a lower molecular weight polysaccharide and a higher molecular weight aggrecan protein. Since gum arabic has good water solubility, it is very simple to prepare, neither heating nor accelerator. The gum arabic dries very quickly. It can be used for bonding of optical lenses, stamping, labeling, labeling of food packaging, and printing and dyeing auxiliaries.

09
Inorganic adhesive

Adhesives made of inorganic materials such as phosphates, phosphates, sulfates, boron salts, metal oxides, etc. are called inorganic binders.
(1) High temperature resistance, can withstand 1000 ° C or higher:
(2) Good anti-aging properties:
(3) Small shrinkage rate
(4) Large brittleness. The modulus of elasticity is one level higher than that of organic adhesive:
(5) Poor resistance to water and acid and alkali.

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