Solid facestock based on reaction mixture having two blowing agents

Abstract

The present invention relates to the provision of a polyurethane-based structural, whole-skin, solid facestock. A reaction mixture comprising a polyol, a polyisocyanate, and at least two different types of blowing agents having different behaviors is provided. The invention also relates to a method for producing the solid surface material from the reaction mixture.

Description

[0001] The present invention relates to providing a structural integral skin solid surface material based on polyurethane. It provides a reaction mixture comprising a polyol, a polyisocyanate and at least two different types of blowing agents with different behaviors. It also relates to a method for producing a solid surface material from the above reaction mixture.

[0002] Recent publications call for the invention of a new solid surface consisting of foamed polyurethane based on aliphatic isocyanates with high light resistance and excellent mechanical properties. Unlike other solid surfaces on the market, this solid surface has an integral sandwich structure with a foamed core and a dense skin. This structure provides better mechanical properties at a lower weight. In order to ensure that the material is durable and allows for multiple repairs by polishing, the skin must be much thicker than conventional integral PU parts that are not prepared to withstand such attacks.

[0003] An efficient and reliable solution to this challenge is proposed here by proposing an innovation that enables obtaining a thicker and more regular skin than presented by commercial polyurethane parts. Such a skin is hard, thick and regular under the different working conditions that may occur in an industrial environment.

[0004] Solid surface materials are defined as materials formed from a polymer matrix, pigments and fillers, which can be processed by sheet forming or molded products. They are also defined in ISO standard 19712-1 UNE.EN:2013. Solid surface materials are homogeneous products, i.e. they have the same composition throughout their thickness. Due to this feature, they can be easily repaired by simple sanding.

[0005] Typically, solid surface materials are used for bathroom and kitchen fixtures such as sinks, toilets or countertops. Currently available solid surface materials contain a polymer matrix made of acrylic or polyester resins. The most commonly used filler is aluminum oxide trihydrate.

[0006] Structural integral skin materials are defined by an isotropic chemical composition but with a large density difference between the center (core) and surface (skin) of the material. Common density ranges in these materials are 1100 to 1400 kg / m in the skin. 3 , and in the core 800 to 400 kg / m 3 .

[0007] Solid surface materials are characterized by a thick skin that allows repeated sanding (eg, to repair damaged surfaces) without damaging the surface.

[0008] Besides casting solid surface materials to give them their final shape, another common route is the manufacture of blanks and subsequent post-production steps such as thermoforming. This means that the final shape of the solid surface material is achieved after the resin has fully cured. Conventional solid surface materials are therefore based on thermoplastic resins. Thermoforming, cutting and gluing are often used to create more complex shapes that cannot be created directly by casting, with the disadvantage of being a time-intensive manual process.

[0009] Conventional solid surface products are usually sensitive to ultraviolet radiation and to acids, alkalis and detergents, so that they cannot be used for outdoor applications without additional radiation protection. In addition, it is known that typical detergents such as isopropyl alcohol may cause stress cracking corrosion. In addition, it is desirable to produce solid surface materials by reaction injection molding (RIM) because this is a fast and efficient method. However, the polymer matrix discussed above is not very suitable for this production method because they need a long curing time of up to two hours. In addition, conventional substrates show high volume shrinkage during curing, which adversely affects dimensional stability, especially in common low-pressure RIM or even casting processes. Therefore, it is desirable to use (i) UV resistance without additional treatment, (ii) have good dimensional stability during curing, and (iii) have a short curing time so that it can be processed by RIM system.

[0010] Solid surface materials based on polyurethane have been described in EP 3 354 669 and WO 2018 / 172413. The preferred method for making these materials is the reaction injection molding (RIM) method. However, when using this method, volume shrinkage during curing is a problem because it causes pores, cavities and deviations of the finished product from the desired shape. EP 3 354 669 proposes a combination of irreversible foaming agents and reversible foaming agents for making such materials. However, as shown in the research on which the present invention is based, simply combining irreversible foaming agents with reversible foaming agents in arbitrary proportions is not enough to produce such materials. The present application is the first document describing the components and reaction conditions required for actually making a material having the properties described in EP 3 354 669.

[0011] Therefore, the problem to be solved by the present invention can be defined as providing a solid surface material having a sandwich structure with a thick integral skin and a foamed core.

[0012] This problem is solved by the embodiments defined by the claims and the following description. Thus, in a first embodiment, the invention relates to a polyurethane component, at least one region of which is characterized by

[0013] (i) Thickness between 8 mm and 50 mm,

[0014] (ii) The average density in the first 1.5 mm below the surface is 0.9 g / cm 3 Up to 1.4g / cm 3 between, and

[0015] (iii) the average density in those polymer parts at least 2.5 mm below the surface is 0.25 g / cm 3 Up to 0.8g / cm 3 between,

[0016] It is obtained or obtainable by polymerizing a composition comprising:

[0017] a) polyol component A1;

[0018] b) a polyisocyanate component A2 comprising at least 60% by weight of aliphatic and cycloaliphatic polyisocyanates;

[0019] c) at least one reversible blowing agent B1;

[0020] d) at least one irreversible reagent B2, and

[0021] e) at least one catalyst C.

[0022] In a preferred embodiment, the composition further comprises at least one additive selected from the group consisting of pigments, flame retardants, dispersants, emulsifiers, cell regulators, foam stabilizers, biocides and inorganic fillers.

[0023] The "polyurethane part" is the product obtained by the reaction of compounds A1 and A2 comprised by the polymerizable composition. In a preferred embodiment of the present invention, the thickness of the polyurethane part is between 8 mm and 50 mm, more preferably between 8 mm and 40 mm, and most preferably between 10 mm and 30 mm.

[0024] Preferably, the area characterized by the thickness and density defined above is measured at least 20 mm, more preferably at least 50 mm in each of the other two dimensions. This does not exclude that other parts of the polyurethane part may be thicker or thinner than this and / or have a density different from the limits given in this application. In order to make the most efficient use of the material, it is particularly preferred that the part has the thickness defined above over at least 50%, more preferably at least 75% of its total area.

[0025] Preferably, the polyurethane component has at least two parallel surfaces. However, it may also have any other shape suitable for the intended use of the polyurethane component. The polyurethane component is preferably a product selected from bathroom fittings, kitchen equipment, housings for electrical and electronic equipment, appliance housings, vehicle components, building components, indoor furniture and outdoor furniture.

[0026] Preferred bathroom fixtures are selected from the group consisting of bathtubs, sinks, toilets, toilet seats, bathroom panels and shower trays.

[0027] Preferred components of kitchen equipment are selected from the group consisting of kitchen sinks, cookers, heated display cabinets, cooktops and ovens.

[0028] Preferred building components are selected from door panels, wall panels, fence panels, skylights, wall cladding, door frames and window frames.

[0029] The preferred electrical appliance housing is selected from the housings of automatic teller machines, refrigerators and washing machines.

[0030] Preferred vehicle components are selected from the group consisting of components for automobiles, airplanes, trains and ships.

[0031] Preferred indoor furniture pieces are selected from the group consisting of shelves, beds, chairs, tabletops and desks.

[0032] Preferred outdoor furniture components are components of garden furniture.

[0033] Due to the combined effect of the blowing agent, the polyurethane part has a higher density near the surface and a lower density in its core due to the stronger foaming. Therefore, in a preferred embodiment of the invention, the material is characterized by an average density of 1.1 g / cm2 in the first 1.5 mm below the surface. 3 Up to 1.4g / cm 3 between.

[0034] As is clear from the description of the manufacturing method below in this application, the density of the material follows a decreasing gradient starting from the highest density at the surface and ending with the lowest density at the center. Therefore, the density in the two areas defined above is not uniform. However, the average density of the core can be easily determined by cutting out a piece of the material at least 2.5 mm below the surface and determining its density.

[0035] Similarly, the density of the surface layer can be easily determined by cutting off a piece of material including the skin and core regions, measuring the thickness of the skin and core and subtracting the weight of the core, whose density is determined as described above, from the total weight of the cut section. Since the density of the material is highest just at the skin and then gradually decreases through the first few millimeters below the skin, the skin density determined above must be an average value.

[0036] A "polymerizable composition" as referred to in this application is a composition comprising the ingredients defined above in such a form that their reaction can be initiated and said reaction results in crosslinking of the polyols and polyisocyanates to produce a polyurethane polymer. Thus, at least components A1 and A2 are present as a homogeneous mixture.

[0037] Reversible foaming agent B1

[0038] A "reversible" blowing agent is a compound that changes from a liquid phase to a gas phase when subjected to a defined temperature and pressure, but returns to the liquid phase when the pressure is increased or the temperature is decreased. Preferably, the reversible blowing agent should be a liquid at atmospheric pressure and room temperature.

[0039] The reversible blowing agent B1 is preferably a liquid having a boiling point at atmospheric pressure between 5 °C and 50 °C, more preferably between 10 °C and 30 °C, and most preferably between 10 °C and 20 °C.

[0040] In a preferred embodiment, the reversible blowing agent B1 has a vapor pressure at 50 °C between 100 kPa and 300 kPa.

[0041] The above properties of the first blowing agent are important for obtaining a foamed material with a dense surface. Once the reaction starts and heat is generated, the blowing agent with these properties evaporates in the center of the polymerizable composition. However, above a certain combination of pressure and temperature, they remain liquid or return to their original liquid state. This occurs near the surface cooled by the surrounding environment. Thus, a lower density foamy structure is formed at the core, and a solid skin with a high density is formed near the surface.

[0042] The preferred reversible blowing agent B1 is an organic molecule having less than 8 carbon atoms and a boiling point at atmospheric pressure between 10 °C and 50 °C.

[0043] The products that can be used as reversible blowing agents for the production of solid surface materials are subdivided into three families:

[0044] 1. Non-halogenated organic compounds: These are molecules that always contain carbon and hydrogen. They are interesting due to their high availability and low price on the market. However, their high flammability / explosiveness makes it necessary to handle them in ATEX facilities and / or in a controlled atmosphere. These molecules are preferably:

[0045] 1a. Partially oxidized hydrocarbons: Contain carbon atoms, hydrogen atoms and at least one oxygen atom in their molecular composition. These products are esters, ethers, ketones, aldehydes and formic acid. Alcohols must be excluded from this group due to their reactivity with isocyanates.

[0046] 1b. Alkanes and cycloalkanes: Contain only carbon and hydrogen atoms, having the formula H B C A , where 1 < A < 8 and B = 2A or B = 2xA + 2. Although they pose a risk due to their high flammability, they are soluble in component A and are not reactive. The preferred compounds of this family are butane, isopentane and cyclopentane.

[0047] 2. Having the general formula C A H B X JHalogenated organic compounds, where 0 < A < 6, H + X = 2xA + 2 and X is F, Cl or Br. These have been used due to their low flammability.

[0048] The subclasses in this second group are

[0049] 2a. CHC chlorinated organic compounds: These compounds have the general formula C A H B Cl J , where 0 < A < 6 and B + J = 2xA + 2. Preferably, it is dichloromethane CH2Cl2.

[0050] 2b. CFCs: Compounds containing chlorine, fluorine and carbon, such as the so-called CFC-11 (CFCl3 trichlorofluoromethane).

[0051] The general formula is C A F J Cl k , where 0 < A < 6 and J + K = 2xA + 2

[0052] 2c. HCFCs: Compounds containing chlorine, fluorine, hydrogen and carbon: Defined by the general formula H B C A F J Cl k , where 0 < A < 6 and B + J + K = 2xA + 2. Preferably, it is the so-called HCFC-22 (HCF2Cl chlorodifluoromethane) with low toxicity.

[0053] 2d. HFC (compounds containing fluorine, hydrogen and carbon): Defined by the general formula H B C A F J , where 1 < A < 6 and B + J = 2xA + 2. Preferably, it is HFC 245 (H3C3F5 pentafluoropropane), HFC 227 (HC3F7 heptafluoropropane) or HFC 365 (H5C4F5 pentafluorobutane). These compounds exhibit a very low ozone depletion potential and are most widely used as polyurethane foaming agents in the world.

[0054] 2e. HFO (hydrofluoroolefins): Defined by the general formula H B C A F J , where 1 < A < 6 and B + J = 2xA, that is, compounds containing at least one unsaturated or double bond as well as fluorine, hydrogen and carbon atoms. These compounds generally have acceptable ozone depletion potential values and global warming potential values.

[0055] Preferably, it is HFO 1100 (H2C4F6 hexafluorobutene) or HFO 1234 (H2C3F4 tetrafluoropropene).

[0056] 3. Organic compounds containing carbon, hydrogen, oxygen and some halogens

[0057] These are characterized by the general formula: C A H B X j O D , where x represents a halogen. There are some ether derivatives in this group.

[0058] Irreversible foaming agent B2

[0059] The term "irreversible blowing agent" refers to a compound or a mixture of at least two compounds that increases in volume when heated from an original temperature to an elevated temperature, but does not exhibit an equal decrease in volume when cooled back to the original temperature. Thus, at least a portion of the volume expansion is permanent and cannot be recovered by cooling back to the original temperature.

[0060] Irreversible blowing agents are preferably based on two mechanisms: The first is the generation of gas due to the decomposition of the compound at elevated temperature, i.e. a chemical reaction rather than just a change of state of matter. Thus, a preferred irreversible blowing agent B2 is a chemical compound which decomposes when heated to the expansion temperature and releases gas in the process.

[0061] The second and preferred irreversible blowing agent is expandable microspheres. The mechanism of these is based on the increase in radius of the solid shell of the material caused by the heating and boiling of the internal hydrocarbon droplets. Once the shell expands, it cannot be reversed to its previous shape by cooling to the original temperature.

[0062] Preferred blowing agents for the first mechanism are compounds that decompose and release gas when heated. These can be organic or inorganic compounds. Preferred inorganic compounds are sodium borohydride, sodium bicarbonate. Preferred organic compounds are azodicarbonamide, oxybis(benzenesulfonylhydrazide), p-toluenesulfonylhydrazide, toluenesulfonylsemicarbazide and 5-phenyltetrazole. Particularly preferred is azodicarbonamide. In order to reduce its activation temperature, salts, especially zinc oxide, can be added.

[0063] In a preferred embodiment, the irreversible blowing agent B2 has an expansion temperature between 70° C. and 150° C. The expansion or activation temperature is the temperature required to increase the volume of the blowing agent at least 10 times at 1013 hPa. The volume increase can be caused by aeration, evaporation of a liquid or generation of gas by a chemical reaction.

[0064] Combination of blowing agents

[0065] The use of a reversible blowing agent A1 together with an irreversible blowing agent B2 is an essential feature of the invention, since only this combination makes it possible to produce a material having the desired sandwich structure.

[0066] The combination of reversible and irreversible blowing agents is essential to the present invention. In the early stages of mold filling, the reversible blowing agent expands to facilitate mold filling, while the irreversible blowing agent selectively expands in the core of the polymerizable composition while remaining inactive near the surface.

[0067] Once the pressure generated by the material during expansion reaches a higher level, the reversible component undergoes a condensation process in the coldest area (surface), remaining in gaseous form in the core. As a result, the product has a low density in the center, which saves material and reduces the overall weight of the product, while maintaining a thick layer of higher density on the surface. This high-density layer makes the product stable in daily use. Without a reversible foaming agent, the polymerizable composition would not completely fill the mold, resulting in a product with a defective shape. Without an irreversible foaming agent, the pressure is lower and the surface condensation of the complementary reversible foaming agent is incomplete, resulting in a thin or poor quality skin.

[0068] The total amount of all blowing agents in the composition is between 2 and 8 liters of blowing agent per kilogram of polymerizable composition, preferably between 3 and 6 liters per kilogram. The "weight of the polymerizable composition" is the total weight when it is filled into the mold, i.e. it includes components a) to e) and all other additives that may be present. The volume of the blowing agent at a temperature of 50° C. and a pressure of 1013 hPa is given if the blowing agent boils or expands completely.

[0069] The studies on which the present invention is based surprisingly showed that products with desirable properties can only be obtained by using a defined ratio of reversible and irreversible blowing agents. Thus, the proportion of reversible blowing agents is 25% to 75% by volume, based on the total amount of blowing agents, the total amount of irreversible blowing agents constituting the remainder being 100% by volume. If both types of blowing agents were to boil or expand completely, their volumes were calculated as the volumes that would exist at a temperature of 50° C. and a pressure of 1013 hPa.

[0070] If the proportion of the reversible foaming agent is higher than 75% by volume, the quality of the skin is too much impaired because there is not enough irreversible foaming agent. A proportion lower than 25% by volume does not improve the skin quality but leads to deterioration of the shape accuracy of the part because the mold is not properly filled.

[0071] Polyol A1

[0072] In the context of the present application, the term "polyol component A1" refers to all organic molecules containing OH groups in the polymerizable composition. Preferably, the polyol component A1 has an average OH functionality per molecule of at least 2, more preferably at least 3 and an OH content of at least 15% by weight or an OH value of at least 500 mg KOH / g. The advantage of a high OH functionality is a high network density of the resulting polymer matrix, thereby providing a high glass transition temperature, which is a key requirement for the desired properties of the resulting solid surface material. Most importantly, the high network density improves the scratch resistance, chemical resistance, hardness and weather resistance of these materials.

[0073] Preferred polyols contained in polyol component A1 are aliphatic, alicyclic, aromatic and heterocyclic polyols. If aromatic polyols are present in polyol component A1, they preferably constitute less than 20% by weight of polyol component A1, more preferably less than 10% by weight, even more preferably less than 5% by weight, and most preferably less than 1% by weight. Preferably, the polyols contained in polyol component A1 exhibit an OH functionality of at least 2. More preferred polyols used in polyol component A1 are selected from diols, glycerol, propylene glycol, butylene glycol, 1,2,10-decanetriol, 1,2,8-octantriol, 1,2,3-trihydroxybenzene, 1,1,1-trimethylolpropane, 1,1,1-trimethylolethane, pentaerythritol, sugars, triethanolamine and polyethers obtained by reacting the above compounds with ethylene glycol and / or propylene oxide. Also preferred are amine-initiated polyols based on polyaspartic acid.

[0074] The stoichiometric ratio of the polyisocyanate component A2 to the polyol component A1 is adjusted to between 0.85 / 1.0 and 1.2 / 1.0, preferably between 0.9 / 1.0 and 1.1 / 1.0, most preferably 1.05 / 1.0.

[0075] Polyisocyanate component A2

[0076] In the context of the present application, the term "polyisocyanate component A2" refers to all organic molecules in the polymerizable composition which comprise at least one isocyanate group. The average isocyanate functionality of all molecules comprised by the polyisocyanate component A2 is at least 1.8 and preferably at least 2.0.

[0077] The term "polyisocyanate" as used herein is a collective term for compounds containing two or more isocyanate groups in the molecule (this is understood by those skilled in the art to mean free isocyanate groups of the general structure -N=C=O). The simplest and most important representatives of these polyisocyanates are diisocyanates. These have the general structure O=C=N-R-N=C=O, where R generally represents an aliphatic, alicyclic and / or aromatic group. Suitable diisocyanates are any diisocyanates that can be obtained in various ways, for example by phosgenation in the liquid or gas phase or by a phosgene-free route, for example by thermal urethane cleavage. Preferred diisocyanates are those with a molecular weight range of 140 to 400.

[0078] When "polyisocyanate" is generally referred to herein, this refers to monomeric and / or oligomeric polyisocyanates equally. However, in order to understand many aspects of the present invention, it is important to distinguish between monomeric diisocyanates and oligomeric polyisocyanates. When "oligomeric polyisocyanate" is referred to herein, this refers to a polyisocyanate formed from at least two monomeric diisocyanate molecules, i.e. a compound that constitutes or contains a reaction product formed from at least two monomeric diisocyanate molecules.

[0079] For example, hexamethylene diisocyanate (HDI) is a "monomeric diisocyanate" because it contains two isocyanate groups and is not the reaction product of at least two polyisocyanate molecules:

[0080]

[0081] In contrast, reaction products formed from at least two HDI molecules and still having at least two isocyanate groups are "oligomeric polyisocyanates" in the context of the present invention. Starting from monomeric HDI, for example, representatives of such "oligomeric polyisocyanates" are HDI isocyanurate and HDI biuret, each of which is formed from three monomeric HDI units:

[0082]

[0083] In the context of the present invention, monomeric isocyanates as well as oligomeric isocyanates are equally useful. However, in a preferred embodiment of the present invention, the oligomeric polyisocyanates constitute at least 5% by weight of the total mass of the polyisocyanate component A2, more preferably at least 10% by weight, even more preferably at least 25% by weight, and most preferably at least 50% by weight.

[0084] In a particularly preferred embodiment of the present invention, the oligomeric polyisocyanate constitutes at least 95% by weight, more preferably at least 98% by weight, of the total mass of the polyisocyanate component A2. Oligomeric polyisocyanate compositions having a low content of monomeric polyisocyanates can be obtained by reacting monomeric polyisocyanates under suitable reaction conditions and subsequently removing the unreacted monomeric polyisocyanates, for example by thin-film distillation.

[0085] Processes for the preparation of oligomeric polyisocyanates suitable for the invention are described, for example, in J. Prakt. Chem. 336 (1994) 185-200, DE-A 1 670 666, DE-A 1 954 093, DE-A 2 414 413, DE-A 2 452 532, DE-A 2 641 380, DE-A 3 700 209, DE-A 3 900 053 and DE-A 3 928 503 or in EP-A 0 336 205, EP-A 0 339 396 and EP-A 0 798 299.

[0086] Particularly suitable for the present invention are selected from 1,4-butane diisocyanate (BDI), 1,5-pentane diisocyanate (PDI), 1,6-hexane diisocyanate (HDI), 2-methyl-1,5-pentane diisocyanate, 1,5-diisocyanato-2,2-dimethylpentane, 2,2,4- or 2,4,4-trimethyl-1,6-hexane diisocyanate, 1,10-decane diisocyanate. , 1,3- and 1,4-cyclohexane diisocyanate, 1,4-diisocyanato-3,3,5-trimethylcyclohexane, 1,3-diisocyanato-2-methylcyclohexane, 1,3-diisocyanato-4-methylcyclohexane, 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (isophorone diisocyanate; IPDI), 1-isocyanato-1-methyl-4 (3)-isocyanatomethylcyclohexane, 2,4'- and 4,4'-dicyclohexylmethane diisocyanate (H12MDI), 1,3- and 1,4-bis(isocyanatomethyl)cyclohexane, bis(isocyanatomethyl)norbornane (NBDI), 4,4'-diisocyanato-3,3'-dimethyldicyclohexylmethane, 4,4'-diisocyanato-3,3',5,5'-tetramethyl Aliphatic or alicyclic polyisocyanates of dicyclohexylmethane, 4,4'-diisocyanato-1,1'-di(cyclohexyl), 4,4'-diisocyanato-3,3'-dimethyl-1,1'-di(cyclohexyl), 4,4'-diisocyanato-2,2',5,5'-tetramethyl-1,1'-di(cyclohexyl), 1,8-diisocyanato-p-menthane, and 1,3-adamantane diisocyanate.

[0087] Preferred aromatic polyisocyanates are selected from 1,3-dimethyl-5,7-adamantane diisocyanate, 1,3- and 1,4-bis(isocyanatomethyl)benzene (xylylenediisocyanate; XDI), 1,3- and 1,4-bis(1-isocyanato-1-methylethyl)benzene (TMXDI) and bis(4-(1-isocyanato-1-methylethyl)phenyl)carbonate, 2,4- and 2,6-toluene diisocyanate (TDI), 2,4'- and 4,4'-diphenylmethane diisocyanate (MDI), 1,5-naphthalene diisocyanate, and combinations thereof.

[0088] The above-mentioned polyisocyanates are equally suitable for use as monomeric polyisocyanates or for the preparation of oligomeric polyisocyanates, which can subsequently be used to prepare the products of the invention.

[0089] Among these polyisocyanates, aliphatic and alicyclic polyisocyanates are particularly preferred. Particularly preferred aliphatic polyisocyanates are selected from 1,6-hexane diisocyanate (HDI), dicyclohexylmethane-4,4'-diisocyanate (H12MDI), isophorone diisocyanate (IPDI), 2,2,4-trimethyl-hexamethylene diisocyanate (TMDI) and pentamethylene diisocyanate 5 (PDI).

[0090] In a particularly preferred embodiment of the present invention, aliphatic and cycloaliphatic polyisocyanates as defined above constitute at least 60% by weight, more preferably at least 80% by weight, even more preferably at least 90% by weight, and most preferably at least 95% by weight of the total mass of the polyisocyanate component A2. In a very particularly preferred embodiment of the present invention, the polyisocyanate component A2 and thus the polymerizable composition are free of aromatic and araliphatic polyisocyanates.

[0091] Suitable oligomeric polyisocyanates are any polyisocyanates having a uretdione, isocyanurate, allophanate, biuret, iminooxadiazinedione and / or oxadiazinedione structure, which are prepared by modification of simple aliphatic and / or cycloaliphatic monomeric polyisocyanates, for example those of the abovementioned type, as described, for example, in J. Prakt. Chem. 336 (1994) 185-200, DE-A 1 670 666, DE-A 1 954 093, DE-A 2 414 413, DE-A 2 452 532, DE-A 2 641 380, DE-A 3 700 209, DE-A 39 00 053 and DE-A 3 928 503 or EP-A 0 336 205, EP-A 0 339 396 and EP-A 0 798 299, or by mixtures of at least two such polyisocyanates. In the production of these polyisocyanates, the actual modification reaction is usually followed by a further process step for removing unreacted excess monomeric diisocyanate.

[0092] In another particularly preferred embodiment of the present invention, the oligomeric polyisocyanate constitutes at least 60% by weight of the polyisocyanate component A2, more preferably at least 80% by weight, even more preferably at least 90% by weight, and most preferably at least 95% by weight. When handling these materials, the use of oligomeric polyisocyanates rather than monomeric polyisocyanates helps to improve safety because the vapor pressure of oligomers is lower than that of monomers.

[0093] According to the invention, a combination of at least two or at least three different monomeric and / or oligomeric polyisocyanates can be used as polyisocyanate component A2.

[0094] In order to adjust the viscosity of the polyisocyanate component A2, it is particularly advantageous to combine at least one monomeric polyisocyanate with at least one oligomeric polyisocyanate. The oligomeric polyisocyanate can be based on the monomeric polyisocyanate used. It can also be based on a monomeric polyisocyanate that is not present as a monomer in the polyisocyanate composition A2. The combination of the above-mentioned oligomeric and monomeric polyisocyanates can also be used to reduce the volume shrinkage of the polymerizable composition during the curing process.

[0095] Catalyst C

[0096] In order to accelerate the reaction, conventional catalysts known in polyurethane chemistry can be used. Therefore, the polymerizable composition further comprises a catalyst C. Suitable as catalyst C is any compound that mediates the formation of urethane groups by isocyanate and polyol. Such compounds are well known to those skilled in the art, for example tertiary amines such as triethylamine, pyridine, picoline, benzyldimethylamine, N,N-endoethylenepiperazine, N-methylpiperidine, pentamethyldiethylenetriamine, N,N-dimethylaminocyclohexane, N,N'-dimethylpiperazine, 1,5-diazabicyclo[4.3.0]non-5-ene (DBN), 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), or metal salts such as iron(III) chloride, tri(ethylacetoacetate)aluminum, zinc chloride, zinc(II) octanoate, zinc(II) 2-ethyl-1-hexanoate, zinc(II) 2-ethylhexanoate, zinc(I) I), zinc (II) stearate, zinc (II) naphthenate, zinc (II) acetylacetonate, zinc (II) amidine complexes, such as Zn(DBU)2(2-ethylhexanoic acid)2 or (1-methylimidazole)2(2-ethylhexanoic acid)2, tin (II) n-octoate, tin (II) 2-ethyl-1-hexanoate, tin (II) ethylhexanoate, tin (II) laurate, tin (II) palmitate, dibutyltin (IV) oxide, dibutyltin (IV) dichloride, dibutyltin (IV) diacetate, dibutyltin (IV) dimaleate, dibutyltin (IV) dilaurate, dioctyltin (IV) diacetate, molybdenum glycolate, or a combination thereof.

[0097] Preferred catalysts C are dibutyltin laurate, zinc neodecanoate and bismuth carboxylates.

[0098] Further preferred catalysts are selected from zinc neodecanoate, bismuth carboxylates, ammonium formate, ammonium acetate, ammonium octoate, tin(II) acetate, tin(II) octoate, tin(II) ethylhexanoate, tin(II) laurate, dibutyltin diacetate, dibutyltin dilaurate, dibutyltin maleate, dimethyltin dineodecanoate, dimethyltin dioleate, laurylmercaptodimethyltin, dioctyltin dineodecanoate, dioctyltin diacetate, bismuth 2-ethylhexanoate, cobalt 2-ethylhexanoate, iron 2-ethylhexanoate, sodium acetate, sodium octoate, potassium formate, potassium acetate, potassium ethylhexanoate, potassium octoate and mixtures thereof.

[0099] The polymerizable composition of the present invention preferably comprises the catalyst as defined above in an amount of 0.01% to 2% by weight in the final composition.

[0100] method

[0101] In another embodiment, the present invention relates to a method comprising the steps of:

[0102] a) providing a polymerizable composition comprising

[0103] (i) polyol component A1;

[0104] (ii) a polyisocyanate component A2 comprising at least 60% by weight of aliphatic and cycloaliphatic polyisocyanates;

[0105] (iii) at least one reversible blowing agent B1;

[0106] (iv) at least one irreversible reagent B2, and

[0107] (v) at least one catalyst C;

[0108] b) injecting the polymerizable composition into a mold;

[0109] c) curing the polymerizable composition at a temperature between 30°C and 90°C.

[0110] The term "providing a polymerizable composition" refers to the process of mixing components A1, A2 and C of the polymerizable composition so that they can react with each other to obtain a polymer. Preferably, components B1 and B2 are also uniformly distributed in the polymerizable composition. This can be achieved by any method known in the art and does not cause any further difficulties.

[0111] The polymerizable composition is then injected into a mold, which is preferably closed and contains only a small opening as a pressure outlet, so that the desired pressure can be reached at the temperature defined in the present application. When the polymerizable composition expands during the subsequent curing step due to the activity of the blowing agents B1 and B2, the mold is preferably only partially filled. Particular preference is given to filling 50 to 85% of the volume of the mold.

[0112] In a preferred embodiment of the invention the mould is shaped to produce a product having a thickness in at least one area measured along the surface normal of between 8 and 50 mm, preferably 8 to 40 mm, and most preferably 10 to 30 mm, wherein said area measures at least 20 mm x 20 mm.

[0113] The temperature of the polymerizable composition is preferably kept in the range between 0°C and 60°C, preferably between 10°C and 50°C during process step b).

[0114] The curing in process step c) is preferably initiated without exposing the polymerizable composition to heat from an external source. Typically, the catalyst present in the composition mediates the formation of urethane bonds. The reaction generated by this method will increase the temperature of the polymerizable composition and thereby accelerate the reaction.

[0115] At the core, the temperature is highest because the heat of reaction cannot be dissipated. The closer to the mold wall (i.e. to the forming surface of the product), the heat decreases because the wall absorbs some of the heat and thus cools the outer layer of the solidified material. This effect is important if a material with a thick skin is required, because the reversible blowing agent B1 expands at the core of the material, but remains liquid or condenses near the wall due to the lower temperature. The density of the material is therefore lower at the core of the product and higher at its surface. This effect is even more pronounced if the mold walls are actively cooled. Therefore, in a preferred embodiment of the method of the invention, the mold walls are cooled so that they are maintained at a temperature between 30°C and 80°C, preferably between 40°C and 70°C.

[0116] Process step c) is carried out until the polymerizable composition is fully cured. This is achieved when it hardens to the point where it is dimensionally stable.

[0117] In another embodiment of the method, the pressure in the mold is controlled to obtain the desired skin thickness.

[0118] Solid Surface Products

[0119] In a further embodiment, the invention relates to a polymer obtained or obtainable by the process of the invention.

[0120] The attached figure shows:

[0121] Figure 1 A cross section of a solid surface material is shown. The average density of region A up to 1.5 mm below the surface is higher than the average density of region B starting at 2.5 mm below the surface.

[0122] The following examples are intended only to illustrate the present invention. They should not limit the scope of the claims in any way. Example

[0123] Example 1: Free foaming in a laboratory or well-ventilated area intended to work under ATEX conditions (explosive atmosphere)

[0124] A mixture consisting of 40 g of the formulation of component A described in Table 1 below was prepared at room temperature. These components contained no water. In a well-ventilated area, the reversible blowing agent was added with manual stirring. It was stirred manually for 30 seconds and the incorporation of gas was observed. A proportional amount of Desmodur - Oligomeric polyisocyanates with an NCO content of 21% by weight based on aliphatic (hexamethylene diisocyanate) and cycloaliphatic (isophorone diisocyanate) isocyanates. The mixture was stirred vigorously, poured into an open paper cup and observed for free foaming.

[0125] Table 1: Compositions for free foaming

[0126]

[0127] NT(Not tested)

[0128] The results show that the incorporation of the tested samples (reversible blowing agents) under energy oscillation is good in all cases.

[0129] In the three cases tested (1, 3, 4), the foaming of the free-foaming container resulted in a volume increase of 2 to 3 times the initial volume.

[0130] The formed domes had smooth surfaces except for CH2Cl2.

[0131] Example 2 Evaluation of sandwich structures in molded form (pilot plant trials using a machine)

[0132] The object of the invention is to achieve a sandwich structure with a thick dense skin and a low-density core in a single operation. In order to verify the effectiveness of these innovations, the core density at different amounts of blowing agent was evaluated in this test. Lower core density leads to more accumulation of material on the outer wall of the test piece to form a thicker skin. The products tested are described in Table 2 below. The order of addition is the same as in the table.

[0133] Table 2: Components used for pilot tests

[0134]

[0135] The components of the previously tempered and homogenized formulation are mixed in a polyurethane injection molding machine. The materials are poured simultaneously and continuously into an aluminum mold tempered at 45°C. When the pouring is complete, the mold is closed. After a few minutes, the mold is opened, the part is removed and stored for 24 hours. The part is trimmed to visualize the cut surface. The extracted parts are subjected to measurements of skin thickness, hardness and quality assessment.

[0136] Table 3: Tested the following component combinations (amounts in g)

[0137]

[0138]

[0139] Formulation A (Comparative): Determination of epidermal density

[0140] A pre-dried resin without a blowing agent is reacted with an isocyanate. Dense non-foamed test pieces and translucent test pieces are obtained. The density of the test pieces is measured by immersion. The density is about 1100 kg / m3. For sandwich components with a foam core, a completely dense skin without microbubbles (as examined with a microscope) can be considered to have a similar local density in the skin area.

[0141] Determination of core density (all examples)

[0142] The core density is calculated as follows: the apparent density of the total part is measured by the Archimedean method (immersion) or by weighing and measuring a rectangular sample. The test piece is cut and the skin formed on each side is inspected and measured by a high-power magnifying glass with an accuracy of 50 microns. If it is uniform and has no bubbles, it is considered to have a density of 1100 kg / m 3 If not, the density is estimated to be lower.

[0143] Knowing the thickness and density of the skin, the weight of the skin is calculated. By mathematical calculation (subtracting the skin weight from the total weight and the skin volume from the total volume), the core density is calculated. This method was tested in specific cases by mechanically removing the skin and measuring the density of the foamed core alone. The correlation proved to be correct.

[0144] result

[0145] Table 4: Compositions 1 and 3 with only one type (comparative)

[0146]

[0147] The lack of an irreversible foaming agent in composition 1 hindered the formation of a dense skin. The absence of a reversible foaming agent in composition 3 made it difficult to fill the mold, even with a special mold with a thickness of only 20 mm.

[0148] Table 5: Composition 2 (comparative)

[0149]

[0150] Low concentrations of irreversible foaming agents produce a slightly foamed skin rather than a dense skin.

[0151] Table 6: Results of Composition 4 (Invention)

[0152]

[0153] In this series of tests, a perfect and relatively thick skin was observed, independently of the density. The core density was proportional to the overall density, with an excellent gradient of core and skin density in all cases, and thus an optimal sandwich structure.

[0154] Table 7: Results of Composition 5

[0155]

[0156] In this series of tests, the ratio between the two blowing agents was increased. The composition still produced an excellent skin, but the core density was higher so that the distribution efficiency of the material was slightly lower.

[0157] A comparison of composition 2 on the one hand and compositions 4 and 5 on the other hand shows that the mere combination of a reversible foaming agent with an irreversible foaming agent is not sufficient to produce a sandwich material with completely satisfactory properties. The concentration of the irreversible foaming agent as well as the ratio of the two foaming agents must be optimized. However, for many applications, the slightly foamed surface obtained with composition 2 is sufficient. This is further analyzed in Example 4.

[0158] Example 3: Machine tests at different thicknesses and shapes

[0159] Three test pieces were made with a step mold to evaluate the material properties at different thicknesses. The formulation used was No. 4 of Example 2. It was filled into a step mold with a thickness of 6 mm, 12 mm, 22 mm and 32 mm and a total volume of 6.0 liters.

[0160] The mould was tilted 15° so that the thickest part was in the upper area to facilitate material flow and filling. The average working temperature of the different components was 45°C. The mould was tempered at the same temperature. The material was mixed in a small pilot continuous batch and mixer. The casting time was 22.5 seconds. Larger machines with higher output should avoid this problem. In any case, the tests carried out showed that the mechanical properties and functionality of the test pieces were not affected.

[0161] Table 8: Results for products with different thicknesses

[0162] Nominal thickness cm 0,5 1 2 3 average Measured thickness mm 6.20 11.50 21.50 31.50 Front skin mm 2.90 2.00 2.20 1.70 Back skin mm 2.90 2.00 1.90 0.70 Apparent density kg / m3 1173 870 730 637 Apr.780 Skin density kg / m4 1200 1150 1100 1050 1100 Core density kg / m5 782 721 643 603 633 Skin hardness Shaw D 80 79 77 82 Core hardness Shaw D 47 42 42 Skin hardness After curing 83.5 82 80 84.5 Core hardness After curing 48 46 46

[0163] The properties of density distribution and skin thickness remain fairly constant with thickness. Although the overall density of the part varies greatly with thickness, the individual densities of the skin and foam are much more stable. For parts with thicknesses between 10 mm and 30 mm, skin thicknesses between 1.7 mm and 2.2 mm are obtained. The skin has a density of approximately 1,100 kg / m 3 density.

[0164] For products with a thickness of 6 mm or less, no sandwich structure is obtained. The weight and the overall or apparent density of the part vary with thickness, but the local density of the surface and the core and the general properties of the material are maintained. It is entirely feasible to produce test pieces with a thickness of 6 mm to 30 mm in the same test piece. The test piece has the desired sandwich structure with a thick and hard skin and a foamed core in all areas where the local thickness is between 10 and 30 mm, without significant defects being observed.

[0165] Example 4: Evaluation of Sandwich Structures in Molded Foam (Laboratory Controlled Conditions)

[0166] In order to control very precisely the parameters of the test parallel to Example 2, a test with the same purpose was carried out under laboratory conditions and manual stirring. In order to verify the effectiveness of these innovations, the manufacture of the material was evaluated in this test while maintaining the same total amount of blowing agent in all samples. Only the ratio of the two blowing agents was varied. The product was manufactured as described below. The order of addition was the same as in the table.

[0167] Table 9: Components used for pilot testing

[0168]

[0169] The tempered components were mixed manually. The mixture was then poured into an aluminum closed mold tempered at 45°C. The mouth of the mold was immediately closed. After a few minutes, the mold was opened, the part was taken out and stored for 24 hours. The part was then trimmed to visualize the internal structure. The extracted parts were measured for skin thickness, hardness and visual quality assessment.

[0170] The actual density of the product is measured by water immersion and compared with the theoretical density of the part completely filling the entire volume of the mold to determine the shape accuracy.

[0171] Table 10: Formulations tested in this example: (amounts in parts by weight) Test amount in gr

[0172]

[0173] Each blowing agent has a different density when expanded, the amounts in liters here taking into account the normal conditions of pressure and temperature (the total amount in liters being constant).

[0174] Test volume in litres

[0175] Reversible foaming agent 2.67 2.04 1.42 0.71 0.00 Irreversible foaming agent 0.00 0.63 1.25 1.96 2.67

[0176] In the case of reversible agents, the formula for an ideal gas is used: PV = nrT, where n = m / Mw. P = 1 Atm, r = 0.082, T = 298 ° K, and Mw in this example is 149.6 g / mol according to the manufacturer's instructions. m is the mass of the reversible blowing agent in grams in the formulation. For irreversible blowing agents, the density of the material after expansion given by the manufacturer is used, in this case 12 g / l.

[0177] Although normal conditions of pressure and temperature have been used in this example; in the wording of the claims, the volumes are fixed at a temperature of 70°C for greater consistency. In all cases, we use Charles' gas law VT=k to convert volumes to other temperatures.

[0178] Table 11: Results

[0179]

[0180] The best relationship of the two blowing agents is achieved when their volumes (not weights) are balanced. The best samples were obtained with formulation LAB3.

[0181] The results show that a minimum amount of 25% by volume of irreversible foaming agent, based on the total volume of the two foaming agents, is required to obtain at least a satisfactory skin quality. A further increase in the proportion of irreversible foaming agent to 75% by volume (experiment 4) further improves the surface quality. Beyond this, no improvement can be achieved. However, increasing the proportion of irreversible foaming agent is also associated with an undesirable effect: the shape accuracy of the molded part is reduced. Therefore, at a proportion of irreversible foaming agent above 75% by volume, the reduced shape accuracy cannot be balanced by the improved surface quality, and this content of irreversible foaming agent is therefore the highest useful amount.

[0182] The reduction in shape accuracy reflects the difficulty in completely and evenly filling the mold. In industrial conditions with large and complex molds, these filling difficulties cause local defects in the product.

Claims

1. A polyurethane part having at least one area measuring at least 20 mm x 20 mm, said area being characterized by (i) Thickness between 8 mm and 50 mm, (ii) the average density in the first 1.5 mm below the surface measured along the surface normal is 0.9 g / cm 3 Up to 1.4g / cm 3 between, and (iii) the average density in those polymer portions at least 2.5 mm below the surface measured along the surface normal is between 0.25 g / cm 3 Up to 0.8g / cm 3 between, It is obtained or obtainable by polymerizing a composition comprising: a) polyol component A1; b) a polyisocyanate component A2 comprising at least 60% by weight of aliphatic and cycloaliphatic polyisocyanates; c) at least one reversible blowing agent B1 which changes from the liquid phase to the gas phase when subjected to a certain temperature and pressure but returns to the liquid phase when the pressure is increased or the temperature is decreased; d) at least one irreversible reagent B2 which increases in volume when heated from the original temperature to an elevated temperature but does not exhibit an equal decrease in volume when cooled back to the original temperature, and e) at least one catalyst C; The volume of the reversible blowing agent is 25% to 75% by volume, the volume of the irreversible blowing agent adds up to 100% by volume, and the volume of the blowing agent is given based on a temperature of 50° C. and a pressure of 1013 hPa.

2. The polyurethane part according to claim 1, wherein the total amount of all blowing agents present in the polymerizable composition is from 2 to 8 liters of blowing agent per kilogram of the polymerizable composition, wherein the volume of the blowing agent is given as stated in claim 1. 3 . The polyurethane part composition according to claim 1 , wherein the reversible blowing agent B1 has a boiling point at atmospheric pressure of between 5° C. and 50° C.

4. The polyurethane component according to any one of claims 1 to 3, wherein expandable microspheres are used as irreversible foaming agents.

5. The polyurethane part according to any one of claims 1 to 4, wherein the irreversible blowing agent B2 has an expansion temperature between 70°C and 150°C. 6 . The polyurethane component according to claim 1 , wherein the polyol component A1 has an average OH functionality per molecule of at least 2 and an OH content of at least 15% by weight.

7. The polyurethane part according to claim 6, wherein the polyol component A1 contains at least one compound selected from diols, glycerol, propylene glycol, butylene glycol, 1,2,10-decantriol, 1,2,8-octantriol, 1,2,3-trihydroxybenzene, 1,1,1-trimethylolpropane, 1,1,1-trimethylolethane, pentaerythritol, sugars, and polyethers obtained by reacting the above compounds with ethylene glycol and / or propylene oxide.

8. The polyurethane component according to any one of claims 1 to 7, wherein the component is selected from bathroom fixtures, kitchen appliances, housings for electrical and electronic devices, appliance housings, vehicle components, building components, indoor furniture and outdoor furniture.

9. A method comprising the following steps a) providing a polymerizable composition comprising (i) polyol component A1; (ii) a polyisocyanate component A2 comprising at least 60% by weight of aliphatic and cycloaliphatic polyisocyanates; (iii) at least one reversible blowing agent B1 which changes from the liquid phase to the gas phase when subjected to a certain temperature and pressure but returns to the liquid phase when the pressure is increased or the temperature is decreased; (iv) at least one irreversible reagent B2 which increases in volume when heated from the original temperature to an elevated temperature but does not exhibit an equal decrease in volume when cooled back to the original temperature, and (v) at least one catalyst C; wherein the volume of the reversible blowing agent is 25% to 75% by volume, the volume of the irreversible blowing agent totals 100% by volume, and wherein the volume of the blowing agent is given based on a temperature of 50° C. and a pressure of 1013 hPa; b) injecting the polymerizable composition into a mold; and c) curing the polymerizable composition at a temperature between 30°C and 90°C.

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