Comparison of Properties of Water-Soluble Polymer and Pectin

Peach glue is a natural polymer compound, the main component of the PS plate protection plate glue, but due to the great difference in the properties of the pectin, it is easy to degenerate and should not be stored, so people are always looking for alternatives to it.

Composition and properties of peach gum
1. Composition

Peach gum, the chemical name of gum arabic, is the secretion of a tropical acacia tree. It can be cut and collected from the stems and branches of trees, and dried and dried. It has various shapes and sizes, including round and egg-shaped. Worm-shaped, white, light yellow or brownish yellow transparent solid, the lighter the color the better the quality; the surface has fine and irregular wrinkles and concave and convex cracks, texture is hard and brittle, there is a strong luster after cracking, its density due to the origin Different but different, roughly between 1.34 and 1.62, the water content does not exceed 15%.

Gum arabic is an organic high-molecular carbohydrate and is a polysaccharide. It is generally composed of D-galactose, L-arabinose, L-rhamnose and D-glucuronic acid, and has a relative molecular weight of about 220,000 to 300,000. Chemical formula XCOOH·XCOOK(XCOO)2Ca·(XCOO)2Mg, wherein X is a sugar (CaH13O5)n consisting of a hydrocarbon oxygen element, n is a very large number, and is arabic acid (X·COO), arabic acid A mixture of calcium [(XCOO)2Ca], magnesium arabinate [(XCOO)2Mg], potassium arabate (XCOOK), English name is Arabicgum, soluble in water, insoluble in ethanol and most organic solvents.

2. Features

(1) Hydrophilicity. The molecular structure of gum arabic consists of -COOH and -OH attached to the same hydrocarbon bond. These two functional groups are hydrophilic and hydroxyl groups

(-OH) accepts moisture more easily than carboxyl (-COOH). So when the gum arabic is dissolved in water, it will dissolve in the process of diffusion-absorption-swelling for about 72 hours to form a molecular solution of the dispersion system. The hydroxyl groups in each molecule are extremely hydrophilic and can be in water. Automatically dissolves into a single-phase stable system that neither condenses nor precipitates, ensuring long-term dispersion stability.

(2) Weakly acidic. Peach gum contains arabic acid (XCOOH), its aqueous solution is weakly acidic, and it reacts with metal or metal oxides to produce arabinates in the presence of alkali and releases hydrogen gas, which has good adsorption.

(3) Corruption. In a hot and humid environment, yeasts are easily propagated and fermented in gum arabic, free arabinic acid, and change the guminess. This is the general nature of sugars, and it is also the reason that gum arabic and long-term use will cause rancid odor. With the increase of temperature, the acidity will increase and the corrosiveness of the metal plate will increase.

The properties of polymer adhesives For more than 20 years, people have sought to find a synthetic polymer that replaces gum arabic as a plate-protecting glue, but it has not been possible to replicate this specific natural rubber. The preparation of colloids close to peach gum requires breakthroughs in water solubility, fluid properties, electrochemical properties, molecular weight, and dispersion properties.

The dissolution of organic compounds has an important condition that the solubility parameters of the solute and the solvent must be similar and that the solubility parameter is close to the necessary condition for the dissolution rather than the sufficient condition. In general, in order to improve the water solubility, it is necessary to introduce enough hydrophilic groups in the molecule, to reduce the crystallinity of the polymer, and to use the counterion force of the polyelectrolyte to promote dissolution. For example, linseed oil is insoluble in water. If maleic anhydride is used for addition reaction, enough carboxyl groups are introduced into the double bonds of linseed oil molecules, and linseed oil becomes water-soluble oil. However, in order to obtain water solubility and introduce the minimum number of polar groups, so far no one formula can be followed, often need to be determined by experiments.

The existence of hydrogen bonds has a good promoting effect on the water solubility, and many polymer compounds obtain water solubility through the association of hydrogen bonds with water molecules. The linear polymer can completely generate hydrogen bonds, allowing water molecules to quickly enter the polymer structure. There are three types of electrochemical properties of water-soluble polymers.

(1) Non-ionic polymers: Polymers that are not ionized in aqueous solution, such as polyethylene glycol, polyethylene oxide, hydroxyethyl cellulose, and oxidized starch.

(2) Anionic polymer: It is anionized in an aqueous solution, such as hydroxymethyl cellulose, sodium polyacrylate, sodium alginate, and the like.

(3) Cationic polymer: It is ionized into cation in aqueous solution, such as quaternary amine polymer, cationic starch, etc.

After many years of practical research, we used (PEO)T monomer to be polymerized in diethylene-ethyl peroxyethyldicarbonate in a polymerizer with refluxing vaporization at a temperature of 58°C for 4 hours. The new type of macromolecule plate-preserving rubber that can replace peach gum, hereinafter referred to as hydrocolloid, has the following molecular structure:

The hydrocolloid is composed of repeating -CH2-CH2-O- building blocks, the 1,2-subunit (-CH2-CH2-) is a hydrophobic group, and the ether bond (-O-) is a hydrophilic group, the oxygen of the ether bond Atoms form hydrogen bonds with hydrogen atoms in water, increasing the solubility of the polymer in water. Furthermore, the oxygen atom in the hydrophilic ether linkage is placed on the outside of the chain, and the hydrophobic ethylene group is placed on the inside, so that the polymer bond becomes easy to bond with water.

New type guard printing glue <br> New type guard printing glue has different two-way function of ink extraction and sealing, and it is made of transparent, odorless, non-perishable, non-precipitating, and its compactness is similar to that of plastic. Membrane" has a strong gas barrier property. The oxygen and nitrogen permeability measured at 25°C is almost zero. It is corrosion-resistant, solvent-resistant, has high tensile strength, and is readily soluble in water. It facilitates manual opening and opening of the machine and sealing. The version is used normally within half a year. The antioxidant rate is 99.7%, the loss of the seal is less than three thousandths, it can be used and stored within the range of -20°C～140°C (the temperature of peach gum is -5°C～45°C), no gel will be produced. Stratification or sedimentation is not easy to crack after sealing.

The amount of new type of sealant is less than 1/3 of that of peach, because the viscosity of peach is 10 Pa·s, and the viscosity of water glue is only 3 Pa·s, which can greatly reduce the cost of single-piece closure. It is 0.1 yuan/block. In addition, the new sealant can also be used to pre-coat the new surface protection to prevent damage to the transport friction and reduce the new scratch rate.

In addition, the research and development of water-soluble polymer materials will be beneficial to the development of water-based inks, water-based varnishes and other environmentally friendly printing materials, and will play a significant role in future development.

Shaanxi Guangcheng Metal Chemical New Technology Co., Ltd. Wang Junhong
Source: "Printing Technology - Equipment and Special Printing"