RU2750385C1 - Composite material for coatings used in metal canning containers - Google Patents

Abstract

FIELD: chemistry.SUBSTANCE: invention relates to the field of chemistry, namely to materials designed for producing coatings of metal canning containers; it can be used for long-term storage of food products, in particular for coatings having direct contact with food products; it can be used for their protection. The composite material is described for coatings, which have direct contact with food products, consisting of complex polyethyropolyols with a hydroxyl number no more than 80 mg KOH/g and acid number no more than 40 mg KOH/g obtained by interaction of a) 35-45 mole % of carboxylic acid component containing: a1) one or several saturated and/or unsaturated aliphatic and/or aromatic carboxylic acids with the number of COON groups = 2 or their anhydrides and a2) aromatic and/or aliphatic monocarboxylic acids; b) 55-65 mole % of alcohol component containing: b1) one or several saturated aliphatic polyatomic alcohols with average OH-functionality a3), crosslinking agents active relatively to OH groups and COOH groups, which are benzguanidine resins or epichlorohydrin adducts with polypropylene glycol or trimethylolpropane, solvent (butanol) and additives, wherein the composite material for coatings, according to this invention, is produced by mixing separate components. A coating of metal canning containers and a substrate for metal canning containers are also proposed.EFFECT: technical result is an increase in coating performance characteristics.6 cl, 2 tbl, 4 ex

Description

The invention relates to materials intended for the production of coatings for metal cans intended for long-term storage of food products, in particular for coatings in direct contact with food products.

Currently, the main share of paints and varnishes for painting the inner surface of metal cans falls on compositions containing epoxydian oligomers.

Despite the fact that such materials make it possible to obtain coatings with good adhesion to metal substrates, sufficient chemical resistance, and elasticity, they have one significant drawback, which is due to the main components of epoxy resins - bisphenol A.

Bisphenol A (BPA), known for its effect on the endocrine system, has been proven that BPA in in vitro tests is mutagenic and small amounts of this substance can pass into packaged food. It is suspected that coatings containing BPA are carcinogenic. Therefore, it is advantageous to use BPA-free coating materials for the interior coatings of metal cans in contact with food.

BPA-free coatings are described, for example, in DE-A 19912794 and EP-A 1277814. However, they are based on solvent-based coating agents with a high solvent content (up to 90% by weight), which is currently undesirable due to emission. Further, solvent residues remaining in the coatings can cause damage to the aggregate due to migration.

Can Coating materials are known, for example, RU 2388776, but they contain as a hardener either blocked polyisocyanates or binders that are synthesized from components that do not comply with GN 2.3.3.97 2-00 "Maximum allowable amounts of substances released from materials in contact with food ", and paragraph 175300 of the USA Code of Federal Regulation Nr. 21, FDA (Food and Drug Administration).

The blocked polyisocyanates cleave off the corresponding blocking agent during baking, for example butanone oxime or ε-caprolactam. However, these fissionable substances can partially remain in the lacquer layer and migrate during storage into the food product. Therefore, such varnish systems are not suitable for use in the food industry. Therefore, it is an object of the present invention to provide BPA-free coating materials that comply with GN 2.3.3.97 2-00 "Maximum Allowable Amounts Released from Materials in Contact with Food" and paragraph 175300 of the USA Code of Federal Regulation Nr. 21, FDA (Food and Drug Administration), and in the cured state also have very good mechanical properties, such as high elasticity, high level of resistance to solvents, chemicals, as well as to fatty and oily substances, and at the same time high resistance to thermal action.

Compliance with the food tolerance in this regard means that only those components are used in the formulation of binders or in the manufacture of the latter, which are listed by GN 2.3.3.97 2-00 "Maximum allowable quantities of substances released from materials in contact with food", and in paragraph 175300 USA Code of Federal Regulation Nr. 21 (FDA).

This is accomplished by the coating materials described below. The subject of the invention is therefore a bisphenol A-free coating composite material for coatings in direct contact with food, comprising:

A) one or more polyester polyamidopolyols with a hydroxyl number of not more than 80 mg KOH / g and an acid number of not more than 40 mg KOH / g, obtained by reaction

a) 45-35 g of a carboxylic acid component containing:

a1) one or more saturated and / or unsaturated aliphatic and / or aromatic carboxylic acids with the number of COOH groups 1 to 2 or their anhydrides; and

a2) if necessary, aromatic and / or aliphatic monocarboxylic acids

b) 50-55 g of an alcohol component containing:

b1) one or more saturated aliphatic polyhydric alcohols with an average OH-functionality of ≤3,

c) 5-10 g of an amine component containing:

c1) aliphatic or cycloaliphatic amines with the number of NH ₂ -groups equal to 2.

B) one or more crosslinking agents active towards OH groups and COOH groups selected from the group consisting of adducts of epichlorohydrin with polypropylene glycol, trimethylolprpan.

B) solvents.

D) aids and additives, if necessary.

The composite coating material according to the invention is made by mixing the individual components A) to D) with each other. This method is another subject of the invention.

In component a1) isophthalic acid, terephthalic acid and phthalic anhydride are used as aromatic dicarboxylic acids or anhydrides of these acids.

As aliphatic dicarboxylic acids used in component a1) adipic acid, dimerized fatty acids obtained by the cleavage of soybean oil, levopimaric acid, obietic acid and maleic acid anhydride.

In component a2), free saturated and unsaturated fatty acids obtained from the cleavage of vegetable oils and methacrylic acid are used as monocarboxylic acids.

In component b1), ethylene glycol, diethylene glycol, neopentyl glycol and trimethylolpropane are preferably used as aliphatic polybasic alcohols.

In component b1), ethylene glycol, diethylene glycol, neopentyl glycol and trimethylolpropane are preferably used as aliphatic polybasic alcohols.

In component b1) hexamethylenediamine and benzoguanamine are used as aliphatic amines

The named compounds of components a1), a2), b1), b2) and c1), respectively, can be used in the respective components individually or in any mixtures with each other.

The preparation according to the invention of the polyester amidopolyol of component A) is carried out in a manner known per se, according to the procedures which are described in detail in Polyesters and alkyd resins. W. Pot.-M. Paint Media 2009, pp. 22-25 or Ullmanns Encyclopaedie der Technischen Chemie, Chemie, Weinheim, 4th edition (1980), vol. 19, p. 61 ff. Or in H. Wagner and HF Sarx Lackkunstharze, Carl Hanser, Munich (1971), pp. 86-152.

The preparation is preferably carried out in the melt, if necessary in the presence of catalytic amounts of conventional esterification catalysts, such as, for example, acids, bases or transition metal compounds such as, for example, tetrabutoxy titanium, dibutyltin oxide, tin octoate, as well as radical polymerization inhibitors such as p-benzoquinone, benzene-1,4-diol, at a temperature of from 80 to 270 ° C, preferably from 100 to 250 ° C, under a nitrogen atmosphere. In this case, the nitrogen flow also serves to remove the water formed in the reaction. If necessary, a separating agent such as, for example, xylene can also be added to carry away the reaction water. The condensation reaction is carried out until the values of the hydroxyl, acid number and nitrogen content, as well as the viscosity value, are reached, to which they strive. In a preferred embodiment of the invention, a polyester amidopolyol containing OH groups is first obtained, which contains small amounts of free carboxyl and amino groups, which are then reacted in the next reaction step with a carboxyl-containing component, such as, for example, phthalic anhydride, with ring opening and formation complex polyesters, and then a free carboxyl group is formed.

The average molecular weight Mw of the polyester amide component A of the present invention of the polyester amidopolyol ranges from 5500 to 7500 amu.

The hydroxyl numbers of the polyesteramidopolyols, component A, according to the invention are in the range of up to 80 mg KOH / g, g, calculated on the solid resin.

The acid numbers of the polyesteramidopolyols, component A, according to the invention are in the range of up to 40 mg KOH / g, calculated on the solid resin.

The nitrogen content of the polyester amide polyols, component A, according to the invention is in the range of up to 1.5% by weight, calculated on the resin solids.

As the compounds of component b) is preferably the reaction product of epichlorohydrin with polypropylene glycol Der ^® 732R (manufactured by Dow Europe GmbH, Stade, Germany) and the reaction product of epichlorohydrin with trimethylolpropane, Der ^® 742 (manufactured by Dow Europe GmbH, Stade, Germany).

The constituents of component E) are, for example, a spill aid, a scratch resistance enhancer, an optical brightener, a light stabilizer, and a solvent.

The desired operating viscosity is usually adjusted by adding organic solvent. Thixotropic additives or combinations of different thixotropic additives, such as polymeric thixotropic additives, can also be used to establish a precisely defined operating viscosity or to achieve special rheological properties.

Another subject of the invention are coatings and coatings on tinplate of the EZhK grade, which are obtained using the coating agent according to the invention and are used for the manufacture of containers, containers and cans for contact with food. EZhK tinplate is coated with a coating agent by varnishing the tape and / or cutting the tape in the form of sheets and / or scroll sheets.

Drying and curing of coatings generally occurs under baking conditions at temperatures up to 240 ° C.

The coatings obtained in this way on tinplate of the EZhK grade are distinguished by particularly good adhesion to metal, high hardness and, at the same time, especially good elasticity, which are in themselves opposite properties. Further, the coatings have very high resistance to solvents, chemicals and water and have good sterilization resistance, good appearance and high gloss. They are free of BPA moieties and are suitable as coatings for food contact cans.

Examples of

The main parameters were determined by the mass fraction of non-volatile substances (according to GOST 31939, weight of the sample 1.0 g, drying time 1.5 h at 140 ° C in a drying chamber with forced ventilation), acid number (mg KOH / g sample, titration NaOH solution with a concentration of 0.1N, in accordance with GOST R 52110), viscosity (viscometer type VZ-246 with nozzle 4, in accordance with GOST 9070), hydroxyl number (mg KOH / g sample, acetylation, hydrolysis, titration with NaOH solution with a concentration of 0.1N, in accordance with GOST R ISO 4327). The acid number and hydroxyl number are indicated for both the supplied form and the solid resin.

The following are used as additives and binders:

- Byk 310 ^®: an aid to wetting of 25% solution in xylene, the firm Byk Chemie, Wesel, Germany.

- Byk 355 ^®: an aid to wetting of 52% solution in methoxypropyl acetate, firm Byk Chemie, Wesel, Germany.

- Ceracol 79 ^®: means to promote scratch resistance, 20% dispersion in monometilovomefiredipropilenglikolya, the firm Byk Chemie, Wesel, Germany.

- Der 732R ^®: curing reaction of the reaction product of epichlorohydrin and polypropylene glycol, company Dow Chemical, Stade, Germany.

- Der 742 ^®: curing agent reaction product of reaction of epichlorohydrin and trimethylolpropane, company Dow Chemical, Stade, Germany.

Example 1

Preparation of polyester amide polyol A1)

332.0 g of diethylene glycol, 110.2 g of neopentyl glycol, 17.3 g of trimethiolpropane were weighed together into a 1.0 L reactor equipped with a stirrer, heating, automatic temperature control device, nitrogen supply, packed column, water separator and receiver, and with stirring and passing nitrogen, heated to 110 ° C. Then 73.7 g of adipic acid, 154.2 g of terephthalic acid, 17.6 g of phthalic anhydride, 12.8 g of maleic anhydride, 2.2 g of levopimaric acid and 40.3 g of benzoguanamine were added. The mixture was heated to 220 ° C so that the column top temperature did not exceed 101 ° C. This separates the reaction water. Condensed to a resin viscosity of 125-130 seconds (the flow time from a VZ-4 viscometer at 20 ° C of a 50% solution in a mixture of butyl cellosolve - methoxypropyl acetate, taken in equimass ratios) and, until the acid number reached no more than 5 mg KOH / g. Then it was cooled to 160 ° C. At this point in the reaction, 120.0 g of sample resin was taken. To the remaining contents of the reactor was added 24.5 g of dimerized fatty acids obtained by cleavage of soybean oil and stirred at 160 ° C until a resin viscosity of 185-190 seconds was reached (flow time from a VZ-4 viscometer at 20 ° C 50% solution in a mixture of butyl cellosolve - methoxypropyl acetate, taken in equimass ratios) and until the acid number reaches no more than 25 mg KOH / g. At this point in the reaction, 120.0 g of sample resin was taken. Then added 225 g of a mixture of butyl cellosolve - Solvesso 150 - methoxypropyl acetate, taken in an equimass ratio, and with stirring was dissolved at 120 ° C for 1.5 hours. Then it was cooled to 60 ° C, the content of the reaction mixture was filtered. Received a solution with a solid content of 66.7 wt. %, acid number 25 mg KOH / g, hydroxyl number 50 mg KOH / g (based on solid resin), with a nitrogen content of 0.5% (based on solid resin), and a viscosity of 200-220 seconds, the flow time from viscometer VZ-4 at 20 ° C.

Example 2

Preparation of polyester amidopolyol A2)

232.5 g of diethylene glycol, 78.9 g of neopentyl glycol and 107.4 g of trimethylolpropane were weighed together into a 1.0 L reactor equipped with a stirrer, heating, automatic temperature control, nitrogen inlet, packed column, water separator and receiver, and with stirring and passing nitrogen, the mixture was heated to 110 ° C. Then 139.2 g of terephthalic acid, 32.8 g of gizophthalic acid, 13.4 g of methacrylic acid, 59.1 g of phthalic anhydride, 38.6 g of maleic anhydride, 2.2 g of obietic acid, 20.5 g of ethylenediamine and 19 , 8 g benzoguanamine. The mixture was heated to 230 ° C so that the column top temperature did not exceed 101 ° C. This separates the reaction water. Condensed to an acid number of <10 mg KOH / g. Then it was cooled to 160 ° C. At this point in the reaction, 120 g of resin (including recovered samples) have been taken. To the remaining contents of the reactor was added 35.7 g of phthalic anhydride and stirred at 160 ° C. until an acid value of 35-45 mg KOH / g was reached. After that, a total of 120 g of resin (including the extracted samples) was taken, then 250 g of a mixture of butyl cellosolve - Solvesso 150 - methoxypropyl acetate taken in an equimass ratio was added, and with stirring, it was dissolved at 120 ° C for 1.5 hours. Then it was cooled to 60 ° C, the contents of the reactor were filtered. Received a solution of complex polyester amide with a solids content of 65.1 wt. %, acid number 37 mg KOH / g, hydroxyl number 75 mg KOH / g (based on solid resin), with a nitrogen content of 0.5% (based on solid resin), and a viscosity of 160-180 seconds, the flow time from viscometer VZ-4 at 20 ° C.

Example 3

Preparation of polyester amide polyol A3)

178.6 g of diethylene glycol, 92.5 g of neopentyl glycol and 142.7 g of trimethylolpropane were weighed together into a 1.0 L reactor equipped with a stirrer, heating, automatic temperature control, nitrogen inlet, packed column, water separator and receiver, and with stirring and passing nitrogen, the mixture was heated to 110 ° C. Then 115.1 g of terephthalic acid, 2.8 g of isophthalic acid, 5.6 g of methacrylic acid, 99.3 g of phthalic anhydride, 24.1 g of maleic anhydride, 0.5 g of levopimaric acid, 0.4 g obietic acid and 17.1 g of benzoguanamine. The mixture was heated to 230 ° C so that the column top temperature did not exceed 101 ° C. This separates the reaction water. Condensed to an acid number of <10 mg KOH / g. Then it was cooled to 160 ° C. At this point in the reaction, 120 g of resin (including recovered samples) have been collected. To the remaining contents of the reactor were added 15.2 g of phthalic anhydride, 4.3 g of free fatty acids of palm oil, 28.9 g of free fatty acids of sunflower oil and stirred at 160 ° C until an acid number of 35-45 was reached. mg KOH / g. After that, a total of 120 g of resin was taken (including the extracted samples), then 250 g of a mixture of butyl cellosolve - Solvesso 150 - methoxypropyl acetate taken in an equimass ratio was added, and with stirring, it was dissolved at 120 ° C for 1.5 hours. Then it was cooled to 60 ° C, the contents of the reactor were filtered. Received a solution of complex polyester amide with a solid content of 64.3 wt. %, acid number 13 mg KOH / g, hydroxyl number 27 mg KOH / g (based on solid resin), with a nitrogen content of 0.5% (based on solid resin), and a viscosity of 160-180 seconds, the flow time from viscometer VZ-4 at 20 ° C.

Example 4: Varnishes and varnish performance tests

Complex polyesteramides according to examples 1 and 2 with vigorous stirring cross-linking agent B) and additives E) at room temperature (examples 3a, 3b and 3c). For comparison, an industrial varnish for coatings of canning containers based on epoxy resins (Der 667 resin and Der 669 resin, taken in a ratio of 3 to 1) and phenol-formaldehyde resin (Phenodure vpr 1785) (example 3 g) were tested.

The ratios of the individual components of the obtained and tested varnishes are shown in Table 1.

The above-described transparent varnishes were applied to plates of tinplate EZhK I class according to GOST 13345, MMK (Magnitogorsk metallurgical plant) using a rod applicator No. 35 and were hot dried for 15 minutes at 190 ° C in a drying oven with air circulation. Films with a thickness of 6.0 -8.0 g / m2 were obtained.

The following technological properties of varnishes were determined: see table. 2.

1) Cross-cut adhesion (according to GOST 15140). Rating: 1 = good, 4 = bad.

2) Determination of impact strength ² (according to GOST 4765)

3) Determination of tensile strength (according to GOST 29309)

4) Two coated plates were stacked on top of each other with the varnished sides facing each other. A black belt filter was placed between the coated plates. Then, for better weight distribution, the stack was covered with a 10 kg steel plate and kept for 16 hours at 60 ° C. After storage, any damage to the film (such as filter paper prints) was visually noted; rating: 0 = good, 5 = bad

5) A cotton swab impregnated with methyl ethyl ketone (MEK) was attached to a hammer weighing 500 g, with a 50 cm long handle and moved with constant pressure on the varnish film, the number of double strokes (back and forth) was determined until severe damage or delamination was observed. The plates were then visually assessed for tarnishing and / or flaking of the film. For better identification of the coating, the test sites were wiped with a cotton swab dipped in a solution of copper sulfate with the addition of hydrochloric acid.

6) The cured coatings were placed in a sterilizer (VK-75-01) for 1.5 hours at 1.2 bar / 120 ° C and then the coatings were tested for loss of adhesion (steaming), loss of gloss, water stains, and bubble formation; rating: 0 = good, 5 = bad.

The discussion of the results:

With the varnishes of examples A1, A2 and A (examples 3a, 3b and 3c) and a conventional varnish of 3 g, coatings with excellent adhesion, high tensile and impact strength, and satisfactory sterilization resistance can be obtained. The solvent resistance (MEK test) and stackability of the conventional varnish are slightly better than those of the varnishes according to the invention. However, the varnishes according to the invention do not contain bisphenol A residues in comparison with the comparative example.

Claims (11)

1. Composite material for coatings in direct contact with food, consisting of polyester polyols with a hydroxyl number of not more than 80 mg KOH / g and an acid number of not more than 40 mg KOH / g, obtained by interaction a) 35-45 mol. % of a carboxylic acid component containing: a1) one or more saturated and / or unsaturated aliphatic and / or aromatic carboxylic acids with the number of COOH groups = 2 or their anhydrides; and a2) aromatic and / or aliphatic monocarboxylic acids; b) 55-65 mol. % alcohol component containing b1) one or more saturated aliphatic polyhydric alcohols with an average OH-functionality a3) crosslinking agents active towards OH-groups and COOH-groups, which are benzguanidine resins or adducts of epichlorohydrin with polypropylene glycol or trimethylolpropane, a solvent - butanol, and additives where the composite coating material is made by mixing the individual components with each other. 2. Composite material according to claim 1, characterized in that the carboxylic acid component is selected from adipic acid, terephthalic acid, phthalic and maleic acid anhydrides, acids, dimerized fatty acids of soybean oil, the alcohol component is selected from diethylene glycol, neopentyl glycol, trimethiolpropane. 3. Composite material according to claim 1, characterized in that component a1) consists of isophthalic acid, terephthalic acid, methacrylic acid, phthalic and maleic acid anhydrides. 4. Composite material according to claim 1, characterized in that component a1) consists of isophthalic acid, terephthalic acid, methacrylic acid, phthalic and maleic acid anhydrides, free fatty acids of palm and sunflower oils. 5. Coating for metal cans, obtained from a composite material according to one of paragraphs. 1-4 for a metal substrate. 6. A coated metal can substrate according to claim 5, wherein the substrate is a metal substrate.