Melamine formaldehyde foam having reduced formaldehyde emission

Abstract

A method for reducing formaldehyde emissions from melamine / formaldehyde polymer articles, films, or fibers by impregnating the articles, films, or fibers with an aqueous solution of at least one formaldehyde scavenger.

Description

Technical Field

[0001] The present invention relates to melamine / formaldehyde foams having reduced formaldehyde emission, methods for producing these foams, and solutions that can be used in these methods.

Background Art

[0002] Elastic foams with closed cells based on melamine / formaldehyde resins, and methods for producing them by heating a foaming agent-containing solution or dispersion of a precondensate of melamine / formaldehyde with hot air, steam or microwave radiation to foam and crosslink are known, for example, as described in EP-A 17672 and EP-A 37470.

[0003] Foams based on formaldehyde resins emit small amounts of formaldehyde. Formaldehyde emission increases with increasing temperature and humidity. Thus, WO 01 / 94436 describes a method for producing a foam based on a melamine / formaldehyde condensate having low formaldehyde emission, in which an MF precondensate having a molar ratio of melamine to formaldehyde greater than 1:2 is used. To achieve very low formaldehyde emission, the foam needs to be further heated at 220 °C for 30 minutes after drying. However, after heating, the foam hardens and cannot be thermoformed.

[0004] US 2008 / 0197524 A1 discloses a method for producing a foam by heating a mixture comprising a melamine / formaldehyde precondensate, a curing agent and a foaming agent to foam and crosslink, where, prior to heating, urea, substituted urea, alkyl- or aryl-substituted melamine, urethane, carboxamide, dicyandiamide, guanidine, sulfurylamide, sulfonamide, aliphatic amine or glycol is added as a formaldehyde scavenger in an amount of 2 to 10% by weight based on the melamine / formaldehyde precondensate.

[0005] In US 7,714,031 B2, it has been shown that formaldehyde emission is reduced by adopting a molar ratio of melamine:formaldehyde exceeding 0.5 when producing a foam from a melamine / formaldehyde initial condensate.

[0006] WO 2018 / 024559 A1 discloses an aqueous polymer dispersion containing a formaldehyde scavenger selected from disodium hydroxysulfonatoacetate, trimethylolpropane triacetoacetate, and malonic dihydrazide in an aqueous anionic-stabilized aliphatic polyurethane dispersion. This polymer dispersion is used for coating or adhering substrates, or preparing films or foils, and impregnating fiber or leather materials.

[0007] On the other hand, WO 2017 / 207687 discloses a method for preparing a polyurethane by reacting a polyisocyanate with a polymer compound having a group reactive with the isocyanate in the presence of a formaldehyde scavenger such as malonic dihydrazide.

[0008] Also, chemical compounds such as 1,2-ethylenebis-acetoacetamide have also been used as Michael donors in flame-retardant compositions. See, for example, WO 2015 / 197744 A1.

[0009] The reduction of formaldehyde emission in known polyurethane foams is not always satisfactory. Furthermore, in order to adjust formaldehyde emission, it is necessary to change the manufacturing method of the polyurethane foam by changing the composition of the reaction mixture while forming the polyurethane foam. This complicates the production of different types of polyurethane foam articles.

Prior Art Documents

Patent Documents

[0010]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Patent Document 6

Patent Document 7

Patent Document 8

Summary of the Invention

Problems to be Solved by the Invention

[0011] The object of the present invention is to provide a simple method for overcoming the drawbacks of the prior art and imparting low formaldehyde emission to molded articles of polyurethane foam and similar polymeric materials.

[0012] Furthermore, the molded article, fiber or foil should show a formaldehyde emission of 0 ppm according to the valid 2019 version of DIN EN 14184-1 and VDA 275.

Means for Solving the Problems

[0013] According to the present invention, this object is achieved by a method of reducing the formaldehyde emission of a melamine / formaldehyde polymer molded article, film or fiber by impregnating the melamine / formaldehyde polymer molded article, film or fiber with an aqueous solution of at least one formaldehyde scavenger.

[0014] Furthermore, this object is achieved by a method for producing a melamine / formaldehyde polymer molded article, film or fiber having low formaldehyde emission, which comprises first producing a melamine / formaldehyde polymer molded article, film or fiber, and then impregnating the surface of the melamine / formaldehyde polymer molded article, film or fiber with an aqueous solution containing at least one formaldehyde scavenger.

[0015] Preferably, the melamine / formaldehyde polymer molded article is made from a melamine / formaldehyde foam.

[0016] Furthermore, this object is achieved by an aqueous solution for impregnating a melamine / formaldehyde foam, which contains a formaldehyde scavenger and does not contain polyurethane, a melamine / formaldehyde polymer, or a mixture, prepolymer or monomer thereof.

[0017] Preferably, the solution contains 0.1 to 25% by mass, more preferably 1 to 25% by mass, of the formaldehyde scavenger based on the total mass of the solution.

[0018] Furthermore, this object is achieved by a method of using this solution for impregnating a melamine / formaldehyde polymer molded article, film or fiber, preferably a melamine / formaldehyde (polymer) foam or a molded article made therefrom.

[0019] Furthermore, according to the present invention, this object is achieved by the following steps: a) preparing a foam from an initial condensate of melamine / formaldehyde; b) annealing the obtained foam at a temperature below 250 °C; c) impregnating the annealed foam with an aqueous solution of a formaldehyde scavenger; d) drying the impregnated and annealed foam. It is achieved by a molded body of melamine / formaldehyde foam that can be obtained and has a formaldehyde emission of 0 ppm determined preferably in accordance with DIN EN 14184-1 and VDA 275. Here, the annealed foam can be shaped before or after impregnation, for example, by cutting or mechanical abrasion of the annealed foam, or For example, the annealed foam is shaped by pressing to obtain a molded body, or For example, the foam is prepared with a mold of a desired shape.

[0020] Furthermore, this object is achieved by a molded body of melamine / formaldehyde foam impregnated with a formaldehyde scavenger selected from acetoacetamide, preferably a molecule containing a covalently bonded acetoacetamide group, and mixtures thereof.

[0021] In the molded body, the amount of the formaldehyde scavenger is preferably 0.025 to 10% by mass based on the impregnated melamine / formaldehyde foam.

Mode for Carrying Out the Invention

[0022] Examples of shaping can be found in Basotect® TG and Basotect® G+.

[0023] The amount of the formaldehyde scavenger or the formaldehyde scavenger solution is preferably 0 to 50% by mass, more preferably 0.025 to 50% by mass, still more preferably 0.05 to 25% by mass, and most preferably 0.1 to 15% by mass based on the dried impregnated molded body.

[0024] The amount of the formaldehyde scavenger compound is preferably 0.025 to 10% by mass, more preferably 0.05 to 5% by mass, most preferably 0.1 to 2.5% by mass, for example 0.1 to 1% by mass based on the molded body, preferably the foam molded article.

[0025] As the formaldehyde scavenger, any suitable formaldehyde scavenger that can reduce the formaldehyde emission from the molded article and form a stable solution in water can be used. Preferably, the formaldehyde scavenger is selected from the group consisting of C-H-acidic compounds and Schiff bases, and C-H-acidic compounds that are Schiff bases.

[0026] For example, the formaldehyde scavenger is selected from the group consisting of acetoacetamide, ethylenediamine bis-acetoacetamide, trimethylolpropane triacetoacetate, malonic acid bis-amide, malonic acid dihydrazide, dimethyl 1,3-acetonedicarboxylate, 6-hydroxyuracil, N-methylacetoacetamide, N,N-dimethylacetoacetamide, 2-cyanoacetoacetamide, methyl cyanoacetate, 2-cyano-N-(2-hydroxyethyl)acetamide, methyl-2-(2-hydroxyethylcarbamoyl)ethanol, urea, substituted urea, alkyl- or aryl-substituted melamine, ureates, carboxamide, dicyandiamide, guanidine, sulfonylamide, sulfonamide, aliphatic amine or glycol, or a mixture thereof.

[0027] Suitable formaldehyde scavengers are disclosed in WO 2017 / 207687, WO 2018 / 024559, WO 2015 / 197744, and US 2008 / 0197524 A1. Preferably, the formaldehyde scavenger is selected from acetoacetamide and compounds containing an acetoacetamide group.

[0028] Most preferably, the formaldehyde scavenger is selected from acetoacetamide and preferably a molecule containing covalently bonded acetoacetamide groups or units, such as ethylenediamine bis-acetoacetamide, N-methylacetoacetamide, N,N-dimethylacetoacetamide, 2-cyanoacetoacetamide. Most preferably, acetoacetamide or ethylenediamine bis-acetoacetamide is used. These compounds act as C-H-acidic compounds and Schiff bases, and thus have a higher reactivity towards formaldehyde compared to other scavenger compounds.

[0029] The formaldehyde scavenger is applied to melamine / formaldehyde polymer moldings, films, or fibers by impregnating the surface of each molded article. Most preferably, the molded article is a melamine / formaldehyde foam impregnated with an aqueous solution. Due to its large internal surface area, a large amount of the aqueous solution can be impregnated into the melamine / formaldehyde foam or a foamed article made of the melamine / formaldehyde foam.

[0030] The aqueous solution generally contains 0.1 to 50% by mass, preferably 0.1 to 25% by mass, more preferably 0.5 to 25% by mass, and most preferably 1 to 20% by mass of the formaldehyde scavenger based on the total mass of the solution.

[0031] In addition to one or more formaldehyde scavengers, the aqueous solution can contain adjuvants such as surfactants or wetting agents, defoamers, and mixtures thereof. When used, the aqueous solution preferably contains up to 20% by mass, more preferably up to 10% by mass of additional components different from water and the formaldehyde scavenger.

[0032] Aqueous solutions containing formaldehyde scavengers are known from the prior art cited above. However, these solutions contain polyurethanes, melamine / formaldehyde polymers, or prepolymers or monomers used in the preparation of polyurethanes or melamine / formaldehyde polymers. According to the present invention, since typically prefabricated polyurethane foams are impregnated, the aqueous solution does not contain polyurethanes, melamine / formaldehyde polymers, or mixtures, prepolymers or monomers thereof. Preferably, the aqueous solution also does not contain additives of ablative flame retardants, such as the gas-forming or water-forming additives disclosed on pages 17 to 19 of WO 2015 / 197744. For example, the aqueous solution does not contain aluminum hydroxide, hydrated aluminum hydroxide, magnesium hydroxide and zinc borate.

[0033] Furthermore, the aqueous solution preferably does not contain polyfunctional Michael acceptors, specifically as disclosed in WO 2015 / 197744.

[0034] More preferably, the aqueous solution according to the present invention does not contain a curing agent and a blowing agent. Melamine / formaldehyde polymer molded articles, films and fibers can be prepared from melamine formaldehyde resins, or preferably melamine formaldehyde foams. They can be prepared by various methods, for example, as disclosed in US 2008 / 0197524 A1, US 7,714,034 B2 and US 2015 / 0210814 A1.

[0035] Suitable melamine / formaldehyde foams and foamed articles are available from BASF SE under the trade name Basotect®. Further reference can be made to EP 0 074 593 A1, EP 0 017 671 A1, EP 0 017 672 A1, EP 0 37 470 A1 for this material.

[0036] It is also possible to prepare melamine / formaldehyde foam according to the process of US 7,714,031 B2. In this way, formaldehyde emission can be further reduced.

[0037] The impregnation can be carried out by any suitable process, such as impregnating the molded article in an aqueous solution containing a formaldehyde scavenger, spraying the aqueous solution onto the molded article, or other processes. The term "impregnation" means bringing the solution into contact with the surface of the molded article such that the formaldehyde scavenger is retained on or within the molded article upon subsequent drying.

[0038] The molded articles, fibers or films obtained according to the present invention, in particular melamine / formaldehyde foams, exhibit low formaldehyde emissions according to DIN EN 14184-1 and VDA 275. Preferably, the emissions are reduced to less than 0.0015 mg / m 3 and more preferably less than 0.0010 mg / m 3 and in particular to 0 ppm. Further, preferably, long-term tests according to the AgBB scheme (German Building Products Health-Related Assessment Committee, AgBB assessment scheme) are met. The present invention will be further illustrated by the following examples.

Examples

[0039] A melamine / formaldehyde foam (Basotect®) was prepared according to Example 2 of US 2015 / 0210814 A1. This foam had a density of 8-10 g / l. Molded articles in the form of foam sheets were cut from the melamine / formaldehyde foam.

[0040] An impregnating solution was prepared by dissolving 1-25% by mass of ethylenediamine-N,N'-bis(acetoacetamide) or acetoacetamide in water. The impregnating active amount refers to the impregnating activity without water, based on the dried foam.

[0041] The following results were obtained regarding the formaldehyde (FA) emission from melamine / formaldehyde foam molded products (Basotect (registered trademark)).

[0042]

Table 1

[0043]

Table 2

[0044] Results of the AgBB test:

[0045]

Table 3

[0046] EA: Ethylenediamine-N,N'-bis(acetoacetamide), expressed as the amount in mass% based on the foam molded product, Basotect (registered trademark) G+: Melamine / formaldehyde foam molded product without impregnation, Maximum value (AgBB): The maximum value allowed in the AgBB test, and the AgBB test was conducted based on the prior art, TVOC: Total volatile organic compounds TSVOC: Total semi-volatile organic compounds

Claims

1. A method for reducing formaldehyde emission from a melamine / formaldehyde polymer molded article made from melamine / formaldehyde foam, comprising impregnating an aqueous solution of at least one formaldehyde scavenger selected from acetoacetamide and compounds containing an acetoacetamide group, and drying.

2. A method for producing a melamine / formaldehyde polymer molded article having low formaldehyde emission, comprising first producing a molded article made from melamine / formaldehyde foam of a melamine / formaldehyde polymer, and then impregnating the surface of the melamine / formaldehyde polymer molded article made from the melamine / formaldehyde foam with an aqueous solution of at least one formaldehyde scavenger selected from acetoacetamide and compounds containing an acetoacetamide group, and drying.

3. A method of using an aqueous solution containing a formaldehyde scavenger selected from acetoacetamide and compounds containing an acetoacetamide group, and not containing polyurethane, melamine / formaldehyde polymer, or mixtures, prepolymers or monomers thereof, for impregnating and drying a melamine / formaldehyde foam molded article.

4. The method of use according to claim 3, wherein the aqueous solution contains 0.1 to 25% by mass of the formaldehyde scavenger based on the total mass of the solution.

5. The following steps: a) preparing a foam from an initial condensate of melamine / formaldehyde; b) annealing the obtained foam at a temperature below 250 °C; c) impregnating the annealed foam article with an aqueous solution of a formaldehyde scavenger selected from acetoacetamide and compounds containing an acetoacetamide group d) drying the impregnated and annealed form; A method for producing a molded article of melamine / formaldehyde foam, comprising:

6. The method according to claim 5, wherein the amount of the formaldehyde scavenger is 0.025 to 10% by mass based on the dried impregnated molded article.

7. In step a), the foam is prepared by the following steps: aa) producing an aqueous mixture (M1) comprising 100 parts by mass of at least one initial condensate of melamine / formaldehyde, 2 to 4 parts by mass of at least one curing agent, 0.2 to 5 parts by mass of a surfactant or surfactant mixture, 0.1 to 5 parts by mass of at least one salt of an inorganic acid or a salt of an organic carboxylic acid, 1 to 40 parts by mass of at least one blowing agent, 0 to 5 parts by mass of at least one dye and / or optical brightener, 0 to 20 parts by mass of one or more further additives, and 25 to 60 parts by mass of water; ab) heating and foaming the mixture (M1) using microwave radiation; ac) crosslinking and curing the obtained foam using the curing agent and microwave radiation; ad) drying the foam using microwave radiation The method according to claim 5 or 6, wherein the foam is prepared by a process comprising the above steps.

8. The method according to any one of claims 5 to 7, wherein the annealed form is molded before or after impregnation.

9. The method or use according to any one of claims 1 to 8, wherein the formaldehyde scavenger is selected from the group consisting of acetoacetamide, ethylenediamine bis-acetoacetamide, N-methylacetoacetamide, N,N-dimethylacetoacetamide, 2-cyanoacetoacetamide, or mixtures thereof.

10. A dried molded body of melamine / formaldehyde foam impregnated with a formaldehyde scavenger selected from acetoacetamide, a molecule containing an acetoacetamide group, and mixtures thereof.

11. The molded body according to claim 10, wherein the amount of the formaldehyde scavenger is 0.025 to 10% by mass based on the impregnated melamine / formaldehyde foam.

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