KR20000008569A - Coating solution compound and coating compound containing it - Google Patents

Abstract

PURPOSE: A composition comprising polyvinyl alcohol, silica compound, silane coupling agent, deforming agent, distilled water in the presence of acid catalyst is provided which has good oxygen blocking property, steam forming resistance,, transparency and antistatic property. CONSTITUTION: The composition comprises 1-20 weight% of polyvinyl alcohol, 0.01-12 weight% of silica compound, 0.01-5 weight% of silane coupling agent, 0.01-10 weight% of deforming agent, and 46-98.97 weight% of distilled water in the presence of acid catalyst selected from hydrochloric acid, sulfuric acid, nitric acid, and acetic acid. The silica compound is selected from tetraethoxysilane, tetramethoxysilane, tetrapropoxysilane, tetrabutoxysilane, glycidoxypropylpremethoxysilane, and methacrylicoxypropyltrimethoxysilane. The silane coupling agent is Qn-Si-Rm where n+m = 4; n,m = a natural number, not 0; R = an organic chain comprising C4-14 with aldehyde or acetal group; Q = hydrolyzable alkoxy. The coating product is obtained by coating the coating solution on polyolefin film with a thickness of 0.1-20 micro meter. The product is useful as a packaging material for foodstuffs and a coating material of packaging material for industrial.

Description

Coating solution compound and coating product containing same

The present invention relates to a coating solution compound and a coating product comprising the same, and more particularly, 1 to 20% by weight of polyvinyl alcohol, 0.01 to 12% by weight of silicon oxide, 0.01 to 5% by weight of silane coupling agent, bubbles under an acid catalyst. A coating solution compound comprising 0.01 to 10% by weight of a removing agent and 46 to 98.97% by weight of distilled water, and a coating product obtained by coating the coating solution compound on a polymer film.

Currently, the packaging film currently used generally does not have good barrier property against oxygen and moisture by itself. Therefore, external oxygen and moisture penetrate into the package to promote oxidation and decay of the package contents, or in the case of package contents requiring a certain moisture content, moisture is released to the outside and consequently extend the shelf life or expiration date of the package. Shortening results in economic and environmental losses. For this reason it is necessary to coat the barrier film on the packaging film to block the penetration of oxygen and moisture.

Various techniques are known using polyvinyl alcohol (PVOH) as a blocking material for the purpose of blocking oxygen and moisture. Polyvinyl alcohol (PVOH) is known as a material having excellent oxygen barrier properties, and is also used as a non-dew-forming coating material due to its strong hydrophilicity. In general, the PVOH coating layer shows excellent oxygen barrier properties and barrier properties to general organic solvents under moisture-free conditions.However, in high humidity conditions, PVOH is a water-soluble polymer, which damages the coating layer due to abrasion and deteriorates the touch. Oxygen barrier has a disadvantage of falling sharply. For this reason, it is necessary to increase the resistance to moisture in order to use PVOH under high humidity.

U.S. Pat. A method of cross-liking PVOH polymer chains to each other is disclosed. As a crosslinking material, a material having an aldehyde group such as melamine-formaldehyde, urea-formaldehyde, glyoxal, glutaric dialdehyde, etc. is used. have. The reaction taking place here is understood to form acetals by reaction of hydroxyl groups and aldehyde groups of PVOH.

In addition, US Pat. No. 5,547,764 discloses a method of improving the resistance to moisture by using a mixture of PVOH having different degrees of hydrolysis. The higher the hydrolysis rate of PVOH, the better the oxygen barrier property, but it is easy to produce fine bubbles during coating and lowers the uniformity of the coating surface during drying. In addition, the higher the hydrolysis rate, the worse the wetting (wetting) to the film base material, the adhesion of the coating layer is lowered to show a decrease in barrier properties. To improve this point, PVOH having a hydrolysis rate of 99% and PVOH of 80 to 90% were used.

U.S. Patent Nos. 5,512,338, 5,506,011, 5,491,023, and 5,151,331 disclose methods for maintaining oxygen barrier properties of PVOH under high humidity using separate moisture barrier layers such as polyvinylidene chloride. .

Korean Patent Laid-Open Publication No. 95-23518 describes a gas barrier film having good water resistance using a mixture of polyvinyl alcohol and poly (meth) acrylic acid.

As described above, since almost all known technologies use only organic materials, the coating film is susceptible to scratching and has limitations in mechanical properties.

These issues have led to Journal of Colloid and Interface Science, Vol, 51, No. 3 A study on the composite materials of tetraalkoxysilane and PVOH or colloidal silica and PVOH has been reported in the paper published in 388-393. In this study, the bond between inorganic particles and PVOH is known as hydrogen bonding between silanol and PVOH on the surface of inorganic particles. However, hybrid materials composed only of inorganic and organic hydrogen bonds, not organic chemical bonds, are easily infiltrated with moisture and have very low resistance to moisture.

As a result of extensive research in order to solve this conventional problem, an organic-inorganic hybrid material obtained by crosslinking inorganic particles and PVOH by chemical bonding using a silane coupling agent has been found, and the present invention has been completed.

It is an object of the present invention to minimize the effect of humidity on the barrier properties by increasing the resistance to moisture of PVOH, to provide a coating solution compound having improved hardness of the coating surface and excellent gloss, low surface electrical resistance.

Still another object of the present invention is to provide a coating product obtained by using the compound.

The compound of the present invention for achieving the above object is 1 to 20% by weight of polyvinyl alcohol, 0.01 to 12% by weight of silicon oxide, 0.01 to 5% by weight of silane coupling agent, 0.01 to 10% by weight of defoamer and 46 to distilled water under acid catalyst. It consists of 98.97 weight%.

The coating product of the present invention for achieving the above another object is a coating product obtained by coating the coating solution with a thickness of 0.1 to 20㎛ the polyolefin film.

As described above, the present invention relates to a barrier coating solution having water resistance, heat resistance, durability, strong surface hardness, and low surface electrical resistance of an inorganic component while maintaining excellent oxygen barrier property and hydrophilicity of the organic component PVOH. .

The polyvinyl alcohol (PVOH) is a solid polymer material, soluble in water but insoluble in most organic solvents. In general, PVOH is obtained by hydrolyzing polyvinylacetate, and the higher the hydrolysis rate of PVOH, the better the barrier property. The hydrolysis rate is more than 85%, and more than 95% in barrier property, flexibility and adhesion. Preferred, most preferably at least 99%. In the present invention, the solid PVOH is dissolved in water at about 80 ° C. to prepare a 5% aqueous solution.

Moreover, as for the viscosity of PVOH, 5-15 cps is preferable at 5 degreeC and 20 degreeC. If the viscosity of the PVOH is too high, it is difficult to form a uniform film due to the increase in the viscosity of the coating solution, so that the viscosity within the above range is suitable.

In the present invention, PVOH is 1 to 20% by weight based on the total coating solution, if less than 1% by weight of the solid content of the film during coating is too small can lead to a decrease in the performance of the coating film, the performance of the coating film even 20% Even if this appears sufficiently, and more than 20, it does not bring improvement in blocking property, so in consideration of economical efficiency, 20 wt% or less is preferable.

As the material having the inorganic component, a silicon oxide prepared by the sol-gel method using silica alkoxide as a precursor is used. Hydrolysis of the silica alkoxide under acid catalyst produces a homogeneous sol solution. Commonly known silica alkoxides include tetraethoxysilane, tetramethoxysilane, tetrapropoxysilane, tetrabutoxysilane, and the like. All such silica alkoxides are usable, but are insoluble in water until hydrolyzed. As the hydrolysis occurs, alcohol is produced and mixed with each other. Considering the residual organic solvents generated during the hydrolysis, the use of ethoxysilane is preferable, and the addition of ethanol may further increase the uniformity of the solution. In addition, organically modified silicate partially substituted with organic materials may be used. However, in the case of simple organic substituents having a large size and no functional groups, the coating agent may be deteriorated by blocking the hydrogen bonding between silanol and PVOH. It has a bad effect. Therefore, the case where it is substituted by simple hydrocarbons, such as a phenyl group and a vinyl group, is not preferable. However, organic substituents containing epoxy groups can be used, such as glycidoxypropyltrimethoxysilane (GPTS).

As said silicon oxide, tetraethoxysilane, tetramethoxysilane, tetrapropoxysilane, tetrabutoxysilane, glycidoxy propyl premethoxysilane, methacryloxypropyl trimethoxysilane, etc. are mentioned, for example. have. In addition, in the present invention, the silicon oxide is 0.01 to 10% by weight based on the total coating solution, if the silicon oxide is not added, the resistance to moisture is lowered, the final physical properties are lowered, and when the content exceeds 10% by weight, the condensation reaction of silicon oxides Due to the increase in viscosity, the stability of the solution is reduced.

The most important feature of the present invention is a silane coupling agent having an inorganic network structure and an alkoxy silane group capable of condensation reaction, and having water as a solvent while having a functional group capable of chemically bonding with a hydroxyl group of PVOH. The silane coupling agent forms a uniform coating layer by suppressing the microphase separation commonly occurring in the organic hybrid material, and is particularly suitable for food packaging materials because water is used as a solvent, and the crosslinking reaction time is also short.

Conventionally, an aldehyde is used as a coupling agent, which is not suitable as a coupling agent of an organic-inorganic hybrid material as a link between organic polymer chains. In addition, in the antifog coating material, the resistance to water may be increased by using a silane coupling agent having a PVOH and an epoxy group, but in this case, the silane coupling agent used should use an organic solvent containing nitrogen, (150 ° C) and a long time (3 hours) are required. The reaction conditions required here are not only economical, but also difficult to apply to general olefinic polymers used for packaging, and the solvents used are suspected to be carcinogens and are not suitable for use in food packaging materials.

The coupling agent can be used as long as it can react with PVOH and convert PVOH into poorly water-soluble. Conventional epoxy resins, melamine resins, metal compounds, fine powder silica, silane coupling agents, and the like, and the like, and in particular, considering the light transmittance of the coating layer, ease of coupling, improvement in hardness, water resistance, and the like, a silane coupling agent is preferable. . For example, 3,3-diethoxypropyltriethoxysilane, 1- (2,2-diethoxyethyl) -4,4-diethoxybutyl triethoxysilane (1 -(2,2-diethoxyethyl) -4,4-diethoxybutyltriethoxysilane (DDBS). Moreover, the silane coupling agent which has a structure of following General formula (1) is the most preferable.

Q _n -Si-R _m

Here, n + m = 4, n and m is a non-zero natural number, R is an organic chain group consisting of 4 to 14 carbon atoms having an aldehyde group or an acetal group, Q is an alkoxy group capable of hydrolysis. As described above, since Q is produced in the form of alcohol during hydrolysis, an ethoxide that generates ethanol is preferable when considering the residual organic solvent after coating. Examples of such a silane coupling agent are as follows.

The silane coupling agent is 0.01 to 5% by weight based on the total coating solution, when the coupling agent is less than 0.01% by weight does not exhibit the function as a coupling agent, when it exceeds 5% by weight brings about reduced barrier properties, economical 5 weight% or less is preferable also from a viewpoint.

In the present invention, an acid catalyst for promoting hydrolysis of the silica alkoxide and the silane coupling agent is used. Generally available acids such as hydrochloric acid, sulfuric acid, nitric acid, acetic acid, and the like, particularly when sulfuric acid is used, shows better barrier properties. If the concentration and amount of the acid used in the present invention is too small, the alkoxy silane is not hydrolyzed well and the reaction does not proceed properly. If too large, the stability of the solution decreases due to the increase in viscosity due to the condensation reaction. Therefore, it is preferable to use in 0.1N concentration and the quantity of 1 ml.

In addition, the coating solution of the present invention further comprises a bubble removing agent. The bubble remover is to prevent the formation of micropores in the coating layer by stirring or coating the solution to prevent the formation of micropores in the coating layer, and to increase the adhesion between the coating agent and the film substrate by reducing the surface tension of the solution, C ₄ ~ C Alcohols of ₁₀ are suitable, in particular 1-octanol.

The amount of the defoamer is preferably 0.01 to 10% by weight based on the total coating solution, if less than 0.01% by weight of the defoamer may result in poor barrier properties due to the deterioration of the film properties due to bubbles generated during coating, Even if it exceeds 10% by weight, since there is no improvement in special functions, 10% by weight or less is preferable in consideration of economical efficiency.

The solid content of the coating solution compound consisting of the above components, that is, the amount contained in the total solution is about 5 to 15% by weight, particularly preferably 8 to 12%. Solid components are PVOH, silicon oxide, coupling agent and defoamer. The proportion of these components is 6 to 90% PVOH, 6 to 90% alkoxysilane, 3 to 30% coupling agent, 0.001 to 0.5% Consists of a defoamer.

The higher the ratio of the solids, the lower the ratio of water (solvent), so that the drying time can be shortened, and the crosslinking reaction between the inorganic substance and the organic polymer also occurs quickly. The higher the proportion of the silane coupling agent, the faster the gelling time of the sol solution tends to be. In addition, since the silane coupling agent reacts with the hydroxyl group of PVOH, the larger the amount of the silane coupling agent, the smaller the amount of the hydroxyl group remaining after the reaction, which tends to show a slight decrease in the barrier property, but the resistance to water tends to be improved. The crosslinking reaction between the silane coupling agent and the PVOH is promoted by an acid catalyst. Since the acid catalyst is used for hydrolysis of the inorganic material, it is not necessary to add a separate acid.

In the method for preparing the coating solution compound of the present invention, first, silica alkoxide and silane coupling agent having different compositions are added to ethanol, and then 0.01N sulfuric acid is added. Thereafter, the reaction is carried out in a magnetic bar stirrer for 1 hour to obtain a uniform and transparent solution in sol state. It is obtained by adding 5% aqueous PVOH solution to this solution and stirring for 30 minutes.

The present invention relates to a coating product obtained by coating a coating solution compound prepared by the above method on a polymer film as described above.

The polymer film in the present invention is a polyolefin-based film made of polyethylene terephthalate (PET), polyethylene, polypropylene, and the like widely used as a general packaging film. Before coating the polymer film with the barrier coating solution prepared above, it is preferable to perform pretreatment to increase the adhesion between the coating layer and the film. The surface tension of the film substrate should be at least 37 dynes / cm as measured according to ASTM standard (D2578-84), with 40 to 45 dynes / cm being preferred. Since the surface tension of polyethylene and polypropylene is about 29 to 33 dynes / cm, the surface treatment of film base is required. In the case of PET, it is about 40 to 43 dynes / cm. Results in a bit. Treatment methods include flame treatment, plasma treatment, chemical treatment, corona discharge treatment, and the like, and corona discharge treatment is particularly preferable.

After such pretreatment, it is more preferred to precoat with a suitable primer to enhance the adhesion between the barrier coating layer and the film substrate. As the primer, a material obtained by condensation of acrylamide or methacrylamide with aminoaldehyde or monoaldehyde may be used, and polyethyleneimine is particularly preferable. The amount of the primer to be used is 0.01 to 3.0 g / m 2, and since it exhibits sufficient performance as a primer without exceeding the above range, it is preferable not to exceed the above range in consideration of economical efficiency. Moreover, the adhesiveness of a coating solution can also be improved by using the film base material containing maleic acid.

The polymer film coated with the primer is dried at 100 ° C. for 5 minutes. The coating solution compound prepared by the method of the present invention on the dried polymer film is coated with a thickness of 0.1 ~ 20㎛. If the thickness is 0.1 탆 or less, the barrier properties are not properly exhibited, and even if the thickness is 20 탆 or more, further performance is not improved.

The coating solution slowly crosslinks the PVOH and the inorganic material by the silane coupling agent, and gradually increases in viscosity when stored at room temperature, and becomes a gel after about 48 to 72 hours. Although it can be seen that the cause of the viscosity increase is caused by the condensation reaction between the inorganic substances, in the embodiment of the present invention, the gel formation takes about 3 to 4 weeks in the case of the solution without only the silane coupling agent. It can be seen that the influence of the silane coupling agent.

The primer coating treatment and the coating solution coating treatment on the film substrate use a bar coater.

In one embodiment of the present invention, the coating solution has a good wetting on the film substrate, and formed a uniform coating layer. The amount of the primer used was 0.01 to 3 g / m 2, and the amount of the coating solution was about 0.2 to 3.0 g / m 2. The coated film substrate was dried in a drying oven at 100 to 130 ° C. The drying time is about 2-20 minutes. During drying, the crosslinking reaction between PVOH and inorganic material and the condensation reaction between inorganic material occur. As these reactions proceed, PVOH's resistance to water increases rapidly and the barrier property increases.

Example 1

The polypropylene (OPP) film stretched to an average thickness of 70 μm was subjected to corona plasma treatment at room temperature and in the air so as to have a surface tension of about 40 dynes / cm. 0.1 wt% of polyethyleneimine was primer-coated on the corona treated film surface, and then dried in an oven at 100 ° C. for 5 minutes. The amount of coated primer was too small to measure, but calculated about 0.05 g / m 2. 5 g of PVOH powder having an average molecular weight of 89,000 to 98,000 and a hydrolysis rate of 99% was put in 95 g of distilled water, and gradually heated to form a clear and transparent aqueous solution. Tetraethoxysilane (TEOS) and 3,3-diethoxypropyltriethoxysilane (DEPS) were added to 5 ml of ethanol at a weight ratio as shown in Table 1, followed by adding 1 ml of 0.01 N sulfuric acid at room temperature for 1 hour. Stirred with a magnetic bar stirrer. To change the weight ratio of TEOS and DEPS according to Table 1 described in Examples 1-1 to 1-6, so added to the prepared 5% PVOH solution was stirred for 30 minutes more. The final coating solution was coated with a bar coater at 5 μm and then dried at 100 ° C. for 10 minutes. The coated polymer films were measured for oxygen permeability according to KS M3052 method at 25 ° C. and 0% and 50% relative humidity, respectively, and the water vapor permeability was measured for one day. After dipping in water for 10 minutes, the loss (%) of the coating layer was measured by weighing before and after dipping in water, and the results are shown in Table 1 below. The amount of solid component after coating is calculated from the weight of the film of 0.1 m 2 area before coating and the weight of the film completely dried after coating.

Example 2

Except for selecting the polymer film polyethylene terephthalate (PET) was carried out in the same manner as in Example 1. Experimental composition and results according to Example 2 are shown in Table 2 below.

Example 3

Instead of 3,3-diethoxypropyltriethoxysilane in Example 2, 1- (2,2-diethoxyethyl) -4,4-diethoxybutyltriethoxysilane (1- (2, Example 2-1, 3-2 and 3-3, respectively, using 2-diethoxyethl) -4,4-diethoxybutyltriethoxysilane (DDBS), except that the compounds were mixed in a weight ratio as shown in Table 3 below. It was carried out in the same way, the oxygen permeability and water vapor permeability and the loss of the coating layer after soaking for 10 minutes in 80 ℃ water is shown in Table 3 below.

Comparative Example 1

Dissolve 1 g of 3,3-diepoxypropyltriethoxysilane in 5 ml ethanol in 5% aqueous solution of PVOH, add 1 ml of 0.01 N sulfuric acid, and stir at room temperature for 2 hours to obtain a coating solution. Except for the same manner as in Example 1. Oxygen permeability experiments showed 0.38 (cc / m 2 · day · atm) at 25 ° C. and 0% relative humidity, and 4.52 (cc / m 2 · day · atm) at 50% relative humidity. The water vapor transmission rate was 2.51 (g / m 2 · day) at 35 ° C.

In the experimental results, the water vapor permeability shows a large difference between the values of Example 1 and Examples 2 and 3, which means that in Example 1, the coating substrate film is biaxially stretched polypropylene (BOPP), and In the case of polyethylene terephthalate (PET), the difference in results due to the difference in the water vapor permeability of the substrate itself is shown.

In Examples 2 and 3, since DDBS has two acetal groups capable of chemically bonding PVOH to molecules and a silyl group capable of bonding inorganic substances at the same time, crosslinking reaction between organic molecules and organic-free Crosslinking reaction of the liver is possible at the same time. Therefore, the formation of a denser coating layer than the DEPS is expected, it was found that even in the actual experimental value better barrier properties than DEPS.

Example 4

A film was prepared by coating on a polyethylene terephthalate (PET) film having an average thickness of 12 μm under the same conditions as in Example 2-6. The antistatic property and the antifogging property of the film prepared by the method of Example 2-6, the film coated only with PVOH, and the untreated PET film were measured and are shown in Table 4 below.

Antistaticity is expressed as the residual half-life time of static charge charged on the film using a static honestmeter. In other words, the shorter the half-life time means the better antistatic performance. Anti-fog can be predicted by measuring the surface tension of the film surface, it was measured by using a corona die test (corona die test) solution, the greater the surface tension indicates that the better anti-fog.

PET film (no treatment) PET film (PVOH only coating) Example 2-6 Static electricity half life (sec) 2325 2238 960 Surface tension (dynes / cm) 40 43 56

As can be seen from the above table, the coating solution containing the polyvinyl alcohol silicon oxide-silane coupling agent provided by the present invention imparts excellent oxygen barrier property, anti-fog property, and antistatic property to the product, such function is Not only can be used as a food packaging material required, it is also useful as a coating agent for industrial packaging materials by properly treating the primer to the product to increase the adhesion of the coating solution to the product while maintaining oxygen barrier properties. In addition, it exhibits excellent oxygen barrier property, anti-fog property, antistatic property, transparency, and can be used for food packaging materials or other uses requiring these properties. In addition, it has high transparency, excellent hardness of coating surface, high barrier property and adhesion of coating film can be maintained for a long time even if the coating layer is thin, and even if mechanical external force is applied to coated product or preserved under high temperature, high humidity, There exists a characteristic which can suppress adhesive fall.

Claims (8)

A coating solution compound comprising 1 to 20% by weight of polyvinyl alcohol, 0.01 to 12% by weight of silicon oxide, 0.01 to 5% by weight of silane coupling agent, 0.01 to 10% by weight of defoamer and 46 to 98.97% by weight of distilled water. The method of claim 1, wherein the silicon oxide is composed of tetraethoxysilane, tetramethoxysilane, tetrapropoxysilane, tetrabutoxysilane, glycidoxypropyl freemethoxysilane, and methacrylicoxypropyl trimethoxysilane Coating solution compound, characterized in that selected from the group. The method of claim 1, wherein the silane coupling agent Q _n -Si-R _m Wherein n + m = 4, n and m are nonzero natural numbers, R is an organic chain group consisting of 4 to 14 carbon atoms having an aldehyde group or an acetal group, and Q is an alkoxy group capable of hydrolysis Coating solution compound. The coating solution compound according to claim 1, wherein the acid catalyst is one selected from the group consisting of hydrochloric acid, sulfuric acid, nitric acid, and acetic acid. The coating solution compound according to claim 6, wherein the acid catalyst is 0.1 N sulfuric acid. The solid content of the coating solution compound is composed of 6 to 90% PVOH, 6 to 90% alkoxysilane, 3 to 30% coupling agent, 0.001 to 0.5% defoamer, Solid solution is a coating solution compound, characterized in that 5 to 15% by weight. A coating product according to claim 1, wherein the coating solution compound is obtained by coating a polyolefin film with a thickness of 0.1 to 20 µm. The coating product according to claim 7, wherein the polyolefin film is made of polyethylene, polypropylene, polyethylene terephthalate, polyamide resin or a compound thereof.