MXPA01004121A - Polyethylene naphthalate polyester polyol and rigid polyurethane foams obtained therefrom - Google Patents

Abstract

Process for preparing a poly(alkylene polyaromatic dicarboxylate)ester based polyester polyol comprising the steps of a) depolymerising poly(alkylene polyaromatic dicarboxylate) in the presence of a glycol and b) transesterifying the obtained product by addition of polycarboxylic acids, anhydrides or esters and/or polyhydric alcohols and use of the thus obtained polyester polyol in the manufacture of rigid polyurethane and urethane-modified polyisocyanurate foams.

Description

POLYETHYL POLYSTYLE OF POLYETHYLENE NAFTALATE AND FOAMS D? RIGID POLYURETHANE OBTAINED FROM EAST Description of the invention This invention relates to the preparation of polyester polyols based on poly (alkylene polyaromatic dicarboxylate ester) and to the use thereof in the preparation of rigid foams of polyurethane and polyisocyanurate. The invention relates more specifically to polyester polyols produced from the reaction of polyethylene naphthalate. The preparation of a rigid polyurethane (PUR) and a polyisocyanurate foam (PIR) by the reaction of a polyisocyanate, a polyol and a blowing agent in the presence of a catalyst is well known. A wide variety of polyols has been used as one of the components in the preparation of rigid polyurethane foams, including polyols from different waste streams. The polyols are usually polyether alcohols or polyester alcohols, or a mixture of the two.The aliphatic and aromatic polyester polyols are in use.These are the reaction products of an esterification of a dicarboxylic acid or an anhydride with glycols. (primary / secondary) Most often a transesterification process is used The aromatic polyester polyols used in rigid PUR / PIR foams are typically based on waste streams of dimethyl terephthalate (DMT) production. Polyethylene (PET) as a source of aromatic carboxylates The depolymerization of waste streams from production or post-consumer waste from eg PET bottles is a known method in the preparation of a polyester polyol. Currently available, made from residues from the PET or DM pieces process T, suffer from a variety of disadvantages such as lack of compatibility with the blowing agents commonly used in the manufacture of rigid PUR / PIR foams. The foams prepared from these polyols are sometimes deficient in the ability to resist compression and / or thermal insulation and / or flame resistance.

It has now been found that polyethylene naphthalate (PEN) can be easily depolymerized and that a polyester polyol with a high content of aromatic material can be made based on this depolymerization product. Rigid polyurethane or polyisocyanurate foams made using this polyester polyol show excellent mechanical stability, good fire performance and low smoke generation with low thermal conductivity. The poly (alkylene polyaromatic dicarboxylate) ester used preferably in the present invention is poly (2,6-naphthalate ethylene). Other isomers of this polymer, or copolymers for example with poly (ethylene terephthalate) (PET), polybutylene terephthalate (PBT) or poly (butylene naphthalate), can also be employed, as well as polyesters based on dicarboxylates with a multiple ring structure (for example, anthracene, phenanthrene) and its copolymers. The polyester polyol is prepared by a two-step process. In a first step, the polyester is depolymerized in the presence of a glycol. This can be, for example, 1,4-butanediol, diethylene glycol (DEG) or dipropylene glycol (DPG). More suitable as the diol is the DEG and it is preferably used in an amount greater than that required for digestion. Although the reaction occurs in the absence of catalysts, the reaction times are significantly shortened by the use of appropriate catalysts. The preferred catalysts are tetra-N-butyltitanate (TBT). Zinc oxide or manganese acetate can also be used. The depolymerization is carried out at a temperature such that the polyester dissociates and the core units are obtained. This is typically in the temperature range of 150 to 350 ° C, preferably of about 240 ° C. The process is typically carried out at atmospheric pressure. However, it will be obvious that pressures higher than atmospheric can be used. At higher pressures, the reaction temperature can be significantly increased, thereby shortening the reaction time. The reaction mixture obtained contains the esterification product from the polyaromatic dicarboxylate and the glycol used, together with the diol of the alkylene chain against the aromatic rings. • Very often, excess glycols are present. When starting with PEN, the product from this first step contains naphthalate polyols, unreacted glycols and ethylene glycol from PEN. During depolymerization and esterification, removal of the ethylene glycol formed by vacuum distillation is possible. This normally results in a lower OH value of the final polyester polyol, together with a reduction in the aliphatic content, which is reflected in the fire performance of the obtained foam. In the present invention ethylene glycol was not removed, without harmful effects on the final properties of the rigid foam. In a second step, the mixture is further transesterified by the addition of other polycarboxylic acids, anhydrides or esters and a polyhydric alcohol. This additional esterification puts the final polyester polyol in the desired viscosity range. The total content of the polyester polymer used in the synthesis of the polyester polyol is typically in the range of 5 to 50% by weight, preferably 10 to 40% by weight. The polycarboxylic acid and the polyhydric alcohol are added at a temperature in the range of 80 to 240 ° C, preferably 100 to 180 ° C. Suitable examples of the polycarboxylic acid component or its derivatives are adipic acid, glutaric acid and glutaric anhydride, succinic acid, oxalic acid, malonic acid, suberic acid, azelaic acid, sebacic acid, phthalic acid, phthalic anhydride, pyromellitic anhydride. . Like polyfunctional alcohol, glycols are preferred. These may be a simple glycol of the general formula CnH2n (OH) 2 or polyglycols with intervening ether linkages, as represented by the general formula CnH2nOx (OH) 2. These may also contain heteroatoms. The polycarboxylic component and the polyhydric alcohol can include substituents which are inert in the reaction, for example the chloro and bromo substituents, and / or can be unsaturated. Examples of suitable polyhydric alcohols are alkylene glycols and oxyalkylene glycols, such as ethylene glycol, diethylene glycol and higher polyethylene glycols, propylene glycol, dipropylene glycol and higher propylene glycols, glycerol, pentaerythritol, trimethylolpropane, sorbitol and mannitol. The two steps described above can also be carried out in a one-step process. The depolymerization of the polyester polymer is the more complete and the faster one uses a two-step process.

The final polyol mixture for the use of the present invention has an average functionality of 1.5 to 8, preferably 2 to 3. The hydroxyl number is generally between 200 and 550 mg of KOH / g of polyol. The molecular weight of the polyesters is generally in the range of 200 to 3,000, preferably 200 to 1,000, more preferably 200 to 800. The term polyester polyol as used herein includes any minor amounts of the unreacted polyol that it remains after the preparation of the polyester polyol and / or the non-esterified polyol. The polyester polyol according to the present invention is used to make a rigid foam based on polyurethane. In the processing of the polyurethane and polyisocyanurate foams, the polyisocyanates and the mixture of isocyanate-reactive components are generally mixed in a one shot method. The high and low pressure techniques can be used in the mixing step. The proportion of the NCO / OH groups generally falls within the range of 0.85 to 1.40, preferably 0.95 to 1.2 for the polyurethane foam, and within the range of 50 to 1, preferably 8 to 1 for the polyisocyanurate foam. In addition to the PEN-based polyester polyol of the present invention, other isocyanate-reactive compounds can be used in the process for the manufacture of rigid polyurethane or urethane-modified polyisocyanurate foams. Suitable isocyanate-reactive compounds include any of those known in the art for the production of rigid polyurethane foams, especially polyether polyols and other types of polyester polyols. In general, the PEN-based polyester polyol of the present invention constitutes between 60 and 100% by weight of the total isocyanate-reactive components. The isocyanate-reactive mixture generally contains polyhydric alcohols and other optional additives such as blowing agents, fire retardants, fillers, stabilizers, catalysts and surfactants. The preferred catalysts for the formation of polyurethane are amines, more preferably tertiary amines. Dibutyltin dilaurate is an example of a non-amine based polyurethanecatalyst. Preferred polyisocyanurate catalysts are alkali metal carboxylates and quaternary ammonium carboxylates. Any of the blowing agents known in the art for the preparation of rigid polyurethane or urethane-modified polyisocyanurate foams can be used in the process of the present invention. The physical and chemical blowing agents can be used, alone or in mixtures. Suitable physical blowing agents are, for example, hydrocarbons, dialkyl ethers, alkyl alkanoates, aliphatic hydrocarbons and cycloaliphatics hydrochlorofluorocarbons, chlorofluorocarbons, hydrochlorocarbons, ethers containing fluorine and carbon dioxide. Examples of preferred blowing agents are isomers of pentane, such as cyclopentane, n-pentane and isopentane, and mixtures thereof, 1,1-dichloro-2-fluoroethane (HCFC 141b), 1,1,1-trifluoro- 2-fluoroethane (HFC 134a), chlorodifluoromethane (HCFC 22), 1, 1-difluoro-3, 3, 3-trifluoropropane (HFC 245fa). The carbon dioxide release products can be used as chemical blowing agents. Water, which releases carbon dioxide after the isocyanate reaction, is widely known as a chemical blowing agent.

The total amount of the blowing agent is typically from 0.1 to 25% by weight, based on the total reaction system. Aliphatic and aromatic polyisocyanates can be used. Aromatic polyisocyanates such as diphenylmethane diisocyanate are preferred (MDI) and toluene diisocyanate (TDI) or the prepolymers thereof. The mixtures of isomers and oligomers can also be used. More preferred is the polymeric form of the MDI. The polyisocyanate can be modified with uretonimine or with carbodiimide. The invention is illustrated, but not limited, by the following examples.

Examples 1-3: Synthesis of the polyester. Into a two liter flask equipped with an efficient stirrer, thermocouple and distillation equipment, diethylene glycol and 2,6-polyethylene naphthalate were charged. 10 ppm of TBT was added. The contents were heated to 240 ° C under efficient stirring and under a nitrogen atmosphere. After 2 to 3 hours, the temperature was lowered to 160 ° C and adipic acid and glycerol were loaded (see table for quantities), together with 10 ppm of TBT. The mixture was heated slowly to 180 ° C and the water was removed by distillation. To complete the esterification, the temperature was further increased to 200 ° C until the theoretical stoichiometric amount of water was removed by vacuum distillation. When the distillation rate was kept constant, a titration of the acid value was carried out. The acid values of 2 mg KOH / gram are acceptable. The specifications of the obtained polyesters are shown in Table 1.

Table 1 Examples 4-7 Rigid foams of urethane-modified polyisocyanurate were prepared from the polyesters made according to examples 1 to 3 above. The formulation components (400 grams) were mixed at 5000 rpm with a small scale laboratory mixing unit, and emptied into an open mold of 20x20x30 cm. HCFC 141b was used as the blowing agent. After standing at room temperature for at least 24 hours, the physical properties of the foams were tested. The ingredients (amounts in parts by weight) and the physical properties of the foam, obtained with the polyols A, B and C and a comparative example based on the PET polyol, are listed in Table 2. Polyol PET: polyester polyol based on PET in pieces, OH value 350 mg KOH / gram. Tegostab B 8406: based surfactant - e_n silicone available from Goldschmidt. TEP: triethylphosphate fire retardant.

DMEA: dimethylethanolamine catalyst. Niax Al: bis (dimethylamino-ethyl ether) catalyst. Dabco K15: potassium octoate catalyst. SUPRASEC 2085: Polymeric MDI available from Huntsman Polyurethanes (SUPRASEC is a brand of Huntsman ICI Chemicals LLC). CT: time of acremado, which is the time in which the mixture changes of appearance of the mixed chemical products, which indicates the beginning of the expansion. ST: string time, which is the time from mixing until the instant in which it is possible to pull a string or polymer strand from the reaction mixture using a spatula. ER: lifting end time, which is the time from mixing to the end of foam expansion. TF: tack-free time, which is the time from mixing until the surface of the foam no longer adheres to a spatula when light pressure is applied. The density was measured according to DIN 53420 standard.

The thermal conductivity was measured according to ISO 2581 standard. The compressive strength was measured according to DIN 53421 standard.

The Kleinbrenner values were determined according to the DIN 4102 standard. The limited 02 index was determined according to the ASTM 2863 standard. The NBS smoke values were determined according to the ASTM E 662 standard.

Examples 8-11 Rigid foams of urethane-modified polyisocyanurate were prepared from the polyesters prepared according to the above examples 1 to 3. The components of formulations (400 grams) were mixed at 5000 rpm and cast in an open mold of 20x20x30 cm. Isopentane was used as the blowing agent. After standing at room temperature for at least 24 hours, the physical properties of the obtained foams were tested. The ingredients (amounts in parts by weight) and the physical properties of the foam, obtained using the polyols A, B and C and a PET-based polyol, are listed in Table 3.

Table 2 Table 3

Claims (9)

1. Process for the preparation of a polyester polyol based on poly (alkylene polyaromatic dicarboxylate ester) comprising the steps of a) the depolymerization of poly (alkylene polyaromatic dicarboxylate) in the presence of a glycol and b) transesterification and polymerization of the product obtained by the addition of polycarboxylic acids, anhydrides or esters and polyhydric alcohols

2. Process according to claim 1, wherein the poly (alkylene polyaromatic dicarboxylate) is poly (2,6-naphthalate ethylene).

3. Process according to claim 2, wherein the poly (2,6-naphthalene ethylene) comes from a production waste stream or a post-consumer waste.

4. Process according to any of the preceding claims, wherein the glycol used in step a) is diethylene glycol.

5. Process according to any of the preceding claims, wherein step a) is carried out in the presence of tetra-N-butyltitanate as a catalyst.

6. Process according to any of the preceding claims, wherein the polyester polyol has an average functionality of 1.5 to 8, hydroxyl number of 200 to 550 mg of KOH / g and a molecular weight of 200 to 3000.

7. Polyester polyol obtained by the process according to any of the preceding claims.

8. Process for the preparation of rigid polyurethane or urethane-modified polyisocyanurate foams, by reacting an organic polyisocyanate with a polyfunctional isocyanate-reactive composition in the presence of a blowing agent, characterized in that the polyfunctional isocyanate-reactive composition comprises a Polyester polyol co or is defined in accordance with claim 7.

9. Process according to claim 8, wherein the polyester polyol constitutes 60 to 100% by weight of the total isocyanate-reactive compounds.