Phosphoric acid ester compositions for flame-retardant soft PVC with low volatility

Abstract

The invention relates to mixtures containing: a) 0 to 30 wt.% (RO)3P=O, b) 10 to 90 wt.% (RO)2(PhO)P=O, c) 10 to 90 wt.% (RO)(PhO)2P=O and d) 0 to 0.5 wt.% (PhO)3P=O, in each case based on the total weight of components a) to d), in which R corresponds to the residue and Ph to the phenyl group. The mixtures exhibit a unique combination of low volatility, high flame retardance, and low melting or softening temperature. The mixtures are therefore particularly suitable for use as flame retardants in PVC compounds, as hydraulic fluids, as lubricant additives, or as additives for paints, adhesives, sealants or coatings.

Description

[0001] Phosphoric acid ester compositions for flame-retardant, low-volatility soft PVC

[0002] Phosphoric acid esters can be used in various technical applications, e.g. as lubricants (cf. US 10,414,964 B2), hydraulic fluids (cf. US 6,703,355 B2), plasticizers (cf. DE 1 768 076) or as flame retardants (cf. US 8,129,457 B2).

[0003] The flame retardant effect of phosphoric acid esters has already been demonstrated in various plastics, e.g. in PVC (cf. GB 2302 543 A), in polyolefins (cf. US 11,008,440 B2), in cellulose esters (US 9,000,148 B2), in polyurethanes (cf. US 8,129,457 B2) or in styrene polymers (cf. US 8,026,303 B2).

[0004] Phosphoric acid esters are particularly important in the processing of soft PVC, where they act both as flame retardants and as plasticizers. Mixed alkyl aryl phosphoric acid esters are frequently used. An example is 2-ethylhexyl diphenyl phosphoric acid ester, known from EP 0 000 240 A1 and marketed as Disflamoll® DPO.

[0005] However, the disadvantages of mixed alkyl aryl phosphoric esters are their lower flame retardancy and higher volatility compared to triaryl phosphoric esters. The latter causes plasticizer loss over the lifetime of a soft PVC article, resulting in undesirable gradual embrittlement.

[0006] Furthermore, state-of-the-art alkyl aryl phosphoric esters, such as Disflamoll® DPO, contain 1 to 5% by weight of triphenyl phosphate. Its hazardous properties have led to increasingly lower levels of this substance being required in consumer applications.

[0007] There has therefore been no shortage of attempts to find improved alkyl aryl phosphoric esters. For example, phosphoric esters based on 2-phenoxyethanol and phenol are known from RT Gottesman et al., Fire Retardants, Proc. Int. Symp. Flammability Fire Retardants 1976, 225-237. The products are described as phosphoric ester compositions, but their components or their quantitative ratios are not disclosed. Likewise, no information is provided about the triphenyl phosphate content or the volatility of the products. Upon reworking the preparation of phosphoric esters based on 2-phenoxyethanol and phenol according to Gottesman et al., it was found that a high triphenyl phosphate content is obtained and that the volatility is in need of improvement.

[0008] The object of the present invention was therefore to provide a mixture characterized by low volatility and a low triphenyl phosphate content, and which achieves a high flame retardancy, particularly in compositions with PVC molding compounds. This mixture should preferably have a low melting point and ideally be liquid at room temperature, thus facilitating processing. Furthermore, this mixture should preferably be obtainable by a low-complexity process and with a low triphenyl phosphate content. In addition, a plasticizing effect in PVC should be achieved.

[0009] The object is achieved by mixtures containing: a) 0 to 30 wt.% (RO)3P=O, b) 10 to 90 wt.% (RO)2(PhO)P=O, c) 10 to 90 wt.% (RO)(PhO)2P=O and d) 0 to 0.5 wt.% (PhO)3P=O, each based on the total weight of components a) to d), preferably each based on the total weight of the mixture, wherein R corresponds to the residue and Ph corresponds to the phenyl residue.

[0010] In a preferred embodiment of the invention, the mixture contains a) 1 to 30 wt. % (RO)3P=O, b) 20 to 84 wt. % (RO)2(PhO)P=O, c) 15 to 79 wt. % (RO)(PhO)2P=O and d) 0 to 0.5 wt. % (PhO)3P=O, in each case based on the total weight of components a) to d), preferably in each case based on the total weight of the mixture. In a further preferred embodiment of the invention, the mixture contains a) 5 to 30 wt. % (RO)3P=O, b) 20 to 80 wt. % (RO)2(PhO)P=O, c) 15 to 75 wt. % (RO)(PhO)2P=O and d) 0 to 0.2 wt. % (PhO)3P=O, in each case based on the total weight of components a) to d), preferably in each case based on the total weight of the mixture.

[0011] In a further preferred embodiment of the invention, the mixture contains a) 10 to 25 wt.% (RO)3P=O, b) 50 to 75 wt.% (RO)2(PhO)P=O, c) 15 to 40 wt.% (RO)(PhO)2P=O and d) 0 to 0.2 wt.% (PhO)3P=O, in each case based on the total weight of components a) to d), preferably in each case based on the total weight of the mixture.

[0012] In a particularly preferred embodiment of the invention, the phosphoric acid ester composition according to the invention contains less than 0.2 wt% triphenyl phosphate, particularly preferably less than 0.1 wt% triphenyl phosphate.

[0013] The mixtures according to the invention are preferably present as solids or as liquids at 23°C and 1013 mbar, particularly preferably as liquids with a dynamic viscosity of 20 to 5000 mPa s, most preferably of 50 to 2000 mPa s (each at 23°C).

[0014] The mixtures according to the invention preferably have a melting or softening point of below 70°C, preferably below 55°C, particularly preferably below 40°C.

[0015] The mixtures according to the invention preferably have an acid number of less than 5 mg KOH / g, preferably less than 1 mg KOH / g, particularly preferably less than 0.3 mg KOH / g, very preferably less than 0.1 mg KOH / g.

[0016] Surprisingly, it has been found that PVC molding compounds containing the mixtures according to the invention exhibit high flame retardancy. The mixtures according to the invention can be produced unexpectedly easily using a novel process such that the mixture contains no or very little triphenyl phosphate.

[0017] Another object of the invention is a process for producing the mixtures according to the invention, comprising the steps:

[0018] (a) providing a mixture containing phosphorus oxychloride and phenoxyethanol,

[0019] (b) reacting at least part of the mixture of a) at temperatures between 0°C and 50°C with separation of hydrogen chloride,

[0020] (c) providing a mixture containing phenol and a base and optionally a solvent,

[0021] (d) combining the mixture obtained from b) and the mixture from c) and reacting at temperatures between -20°C and 50°C to form a chloride salt.

[0022] In an alternative embodiment, at least a portion of the phosphorus oxychloride is added only in step b). It is also possible that at least a portion of the phenoxyethanol is added only in step b).

[0023] The reaction according to step b) is usually carried out in the range from 0°C to 50°C, preferably in the range from 10°C to 40°C, particularly preferably in the range from 20°C to 30°C.

[0024] Optionally, between step b) and step c), a distillative separation of (unreacted) reactants from step a) and / or by-products formed (such as hydrogen chloride) can take place. The distillation can be carried out as a batch process or as a continuous process. The distillation temperature is preferably in the range from 0°C to 50°C. Particular preference is given to carrying out the distillation at the reaction temperature of step b) or a temperature between 0°C and the reaction temperature of step b). The distillation is carried out in a pressure range from 0.01 mbar to 1013 mbar, preferably in the range from 0.01 mbar to 100 mbar, very particularly preferably in the range from 0.01 mbar to 50 mbar.

[0025] All commercially available bases known to the person skilled in the art can be used as the base for step c). These include alkali hydroxides such as NaOH, KOH or LiOH, or amines such as triethylamine, imidazole, 1-methylimidazole, diisopropylethylamine, dibutylamine, morpholine, etc., including ammonia or ammoniacal solutions. In a preferred embodiment, a solvent is used for the reaction in step c). All commercially available solvents known to the person skilled in the art can be used as the solvent. These include, for example, water, aromatic hydrocarbons such as toluene, xylene, aliphatic hydrocarbons such as pentane, hexane, cyclohexane, heptane or longer-chain hydrocarbons, or chlorinated hydrocarbons such as dichloromethane, dichloroethane or chlorobenzene.

[0026] In an alternative embodiment, at least a portion of the mixture prepared in step c) is added to the mixture obtained in step b). It is also possible for at least a portion of the base or a portion of the phenol to be added only in step d).

[0027] The reaction according to step d) is usually carried out in the range from -20°C to 50°C, preferably in the range from 0°C to 30°C.

[0028] After step d), the reactants and / or by-products of steps b) and / or d) can be separated by filtration, extraction, washing, and / or distillation. In a preferred embodiment of the invention, the chloride salts formed as co-products are first separated. If water was used as an optional solvent in step c), the separation can be achieved by simply separating the aqueous and organic phases. If step c) was carried out anhydrous, the chloride salts can be separated by filtration.

[0029] For further purification, the product can be subjected to washing. Suitable washing solutions include caustic soda, potassium hydroxide, or water. Washing is typically carried out at temperatures between 20°C and 50°C.

[0030] The solvent optionally used in step c) can be removed by distillation. The distillation conditions can be easily determined by a person skilled in the art.

[0031] Depending on the application, the mixtures according to the invention may contain further auxiliaries. Examples of auxiliaries include plasticizers, plasticizing polymers, polymeric modifiers, stabilizers (e.g., thermal stabilizers, light stabilizers, antioxidants), co-stabilizers (e.g., acid scavengers, free-radical scavengers), internal and external lubricants, viscosity regulators, fillers, color pigments, dyes, flame retardants, flame retardant synergists, blowing agents, and other functional additives such as antistatic agents, nucleating agents, UV stabilizers, or biocides (see, for example, RD Maier, M. Schiller, Handbook of Plastics Additives, 4th edition, Munich, Carl Hanser Verlag, 2016, p. 513 ff.).

[0032] The mixtures according to the invention are suitable as flame retardants. The present invention thus further relates to the use of the mixtures according to the invention as flame retardants.

[0033] The mixtures according to the invention can be used as flame retardants in all applications for flame retardants known to those skilled in the art. The mixtures according to the invention are preferably used as flame retardants for synthetic polymers, such as polyolefins, polyvinyl chloride, polycarbonates, styrene-based (co)polymers, polyamides, polyesters, polyurethanes, elastomers such as NBR, CR, SBR, or EPDM, and thermosets such as epoxy resins, unsaturated polyester resins, and phenol-formaldehyde resins.

[0034] - Materials of plant origin, such as wood, wood-plastic composites, paper and cardboard, and

[0035] - Materials of animal origin, such as leather, are used.

[0036] The mixtures according to the invention are particularly preferably used as flame retardants for polyvinyl chloride (PVC), for example in PVC molding compounds, ie in compositions containing PVC which are in the form of a granulate, a powder, a paste or a plastisol.

[0037] The invention therefore also relates to compositions, preferably in the form of granules, a powder, a paste, or a plastisol, containing a mixture according to the invention and polyvinyl chloride (PVC). These PVC molding compositions according to the invention are preferably plasticized PVC. The PVC molding compositions according to the invention can be produced by mixing and compounding PVC with the mixtures according to the invention and, if appropriate, further auxiliaries, e.g., stabilizers, in a manner known per se (see, for example, G. Becker, D. Braun, Kunststoff-Handbuch, Polyvinylchlorid, Vol. 2 / 2, Munich, Vienna, Carl Hanser Verlag, 1986, p. 829 ff.) or by dispersing the mixture to form a ready-to-process plastisol or organosol.

[0038] The PVC molding composition according to the invention preferably contains 5 to 150 parts by weight, particularly preferably 30 to 70 parts by weight, of phosphoric acid esters (RO)3P=O, (RO)2(PhO)P=O, (RO)(PhO)2P=O, and (PhO)3P=O according to the invention as defined above, based on 100 parts by weight of PVC. In a preferred embodiment, the PVC molding composition according to the invention contains 5 to 150 parts by weight, particularly preferably 30 to 70 parts by weight, of phosphoric acid esters according to the invention, based on 100 parts by weight of PVC.

[0039] The PVC molding compound according to the invention is used in coatings, films, cables, pipelines, hoses, seals, conveyor belts, roofing membranes, adhesive tape films, tarpaulins, awnings and tents.

[0040] The invention further relates to the use of the mixtures according to the invention in hydraulic fluids or for the production of hydraulic fluids. The mixtures according to the invention are preferably used in flame-retardant hydraulic fluids.

[0041] The invention further relates to the use of the mixtures according to the invention as lubricant additives. The mixtures according to the invention are preferably used in flame-retardant lubricants.

[0042] A further object of the invention is the use of the mixtures according to the invention as additives for paints, adhesives, sealants and coatings.

[0043] The invention further relates to the use of the mixtures according to the invention as heat transfer media or in preparations used as heat transfer media. The mixtures according to the invention are preferably used as heat transfer media or in heat transfer media preparations for immersion cooling of electrical components. In addition to the mixtures according to the invention, the heat transfer media preparations contain, for example, other trialkyl phosphates, triaryl phosphates, mineral oils, polyalphaolefins, esters, antioxidants, metal deactivators, flow additives, corrosion inhibitors, foam inhibitors, demulsifiers, and / or pour point depressants. Determination of the composition of the phosphoric ester compositions

[0044] Quantitative GC-FID analysis was performed using an Agilent 7890A GC equipped with a CB-Sil 5 CB quartz capillary column (length: 30 m, diameter: 0.32 mm, path length: 3.00 μm). Hydrogen was used as the carrier gas. The sample (dissolved in acetone) was injected in split mode (86:1) at a temperature of 300°C. The following temperature program was set: 60°C starting temperature, heating rate 10°C / min up to a temperature of 150°C, then with a heating rate of 25°C / min to 280°C, holding time: 10 min, then with a heating rate of 25°C / min to a final temperature of 320°C / min, holding time: 10 min. The evaluation was performed by integrating the corresponding baseline-separated signal and converting the peak areas into a concentration after prior calibration.

[0045] Determination of the viscosity of phosphoric acid ester compositions

[0046] The dynamic viscosity of phosphoric acid esters was measured using an Anton Paar shear rheometer of type MCR 102 at the specified temperature with a shear rate of 200 s -1 according to DIN 53018.

[0047] Determination of the acid number of phosphoric acid ester compositions

[0048] The acid number of the samples was determined according to DIN EN ISO 2114 (Method B, colorimetric titration with phenolphthalein). For this purpose, the sample (10 g) was weighed, dissolved in acetone (200 mL) and water (50 mL), and 2-3 drops of a phenolphthalein solution (0.1 wt% in ethanol / water (v / v = 4 / 1)) were added. Sodium hydroxide solution (0.1 mol / L) was titrated from a burette until the color change from colorless to pink persisted for at least 10 seconds while stirring. A blank value was measured in the same way, but without the sample.

[0049] Comparative example 1 (V1)

[0050] Herstellung in Anlehnung an R. T. Gottesman et al., Fire Retardants, Proc. Int. Symp. Flammability Fire Retardants 1976, 225-237:

[0051] Phosphorus oxychloride (200 parts by weight) was initially charged into a reactor equipped with a stirrer, internal thermometer, nitrogen inlet, and reflux condenser. Phenoxyethanol (182 parts by weight) was added. The resulting reaction product was reacted with a solution of sodium hydroxide (129 parts by weight), phenol (245 parts by weight), and water (600 parts by weight), yielding a two-phase reaction mixture. After separating the phases, the organic phase was washed with sodium hydroxide solution (0.5 mol / L; 500 parts by weight) and then with water (500 parts by weight). Volatile components were removed by distillation at 50°C and 20 mbar. The product mixture was isolated as a solid (melting point: 73°C). The acid number was 0.1 mg KOH / g. The phosphoric acid ester composition was 0.5 wt% (PhenoxyethylO)3P=O, 13.7 wt% (PhenoxyethylO)2(PhO)P=O, 84.8 wt% (PhenoxyethylO)(PhO)2P=O and 1.0 wt% (PhO)3P=O (“TPP”).

[0052] Inventive Synthesis Example 1 (S1)

[0053] Phosphorus oxychloride (200 parts by weight) was placed in a reactor equipped with a stirrer, internal thermometer, nitrogen inlet, and reflux condenser. Phenoxyethanol (271 parts by weight) was added at a rate such that the internal temperature was maintained between 20°C and 25°C. After the addition was complete, the pressure in the apparatus was gradually reduced from atmospheric pressure to 10 mbar and maintained under final conditions for 1 h. The reaction mixture was added at 0°C to a mixture of dichloromethane (401 parts by weight), phenol (210 parts by weight), and triethylamine (251 parts by weight), while maintaining the internal temperature between 0°C and 15°C. The solid was filtered off, and the filtrate was washed three times with sodium hydroxide solution (2%, 500 parts by weight) and three times with water (500 parts by weight). The solvent was removed by distillation at 90°C and 20 mbar. The product mixture was isolated as a solid (melting point: 54°C). The acid number was < 0.1 mg KOH / g.The product mixture contained 5.3 wt% (PhenoxyethylO)3P=O, 43.1 wt% (PhenoxyethylO)2(PhO)P=O, 51.6 wt% (PhenoxyethylO)(PhO)2P=O and < 0.1 wt% (PhO)3P=O (“TPP”).

[0054] Inventive Synthesis Example 2 (S2)

[0055] Phosphorus oxychloride (201 parts by weight) was placed in a reactor equipped with a stirrer, internal thermometer, nitrogen inlet, and reflux condenser. Phenoxyethanol (361 parts by weight) was added at a rate sufficient to maintain the internal temperature between 20°C and 25°C. After the addition was complete, the pressure in the apparatus was gradually reduced from atmospheric pressure to 10 mbar and maintained at final conditions for 1 h. The reaction mixture was added at 0°C to a mixture of dichloromethane (401 parts by weight), phenol (186 parts by weight), and triethylamine (222 parts by weight), while maintaining the internal temperature between 0°C and 15°C. The solid was filtered off, and the filtrate was washed three times with sodium hydroxide solution (2%, 500 parts by weight) and three times with water (500 parts by weight). The solvent was removed by distillation at 90°C and 20 mbar. The product mixture was isolated as a viscous liquid (330 mPa s at 23°C). The acid number was < 0.1 mg KOH / g.The product mixture contained 20.8 wt% (PhenoxyethylO)3P=O, 58.9 wt% (PhenoxyethylO)2(PhO)P=O, 20.3 wt% (PhenoxyethylO)(PhO)2P=O and < 0.1 wt% (PhO)3P=O (“TPP”).

[0056] Table 1 : Amounts used and analytical data of the synthesis examples V1 , S1 and S2. Production of soft PVC

[0057] The soft PVC molding compounds used for testing were produced on a laboratory rolling mill. After adding the mixture of all formulation components (see Table 2), the mixture was left on the mill until a sheet formed. From this point on, the compounds were compounded on the mill for a further 10 minutes and finally removed as a rolled sheet. The rolling temperature was 165°C.

[0058] The test specimens for determining the LOI were produced from the rolled sheets using a press. The press temperature was 170°C, and the press time was 4 minutes for preheating at low pressure (< 10 bar) and 2 minutes at high pressure (> 100 bar). Test specimens measuring 90 x 13 x 4 mm were sawn from the 4 mm thick press sheets.

[0059] The test specimens used to determine the hardness of the compounds (50 x 40 x 6 mm) were pressed for a longer time at the same temperature due to their large thickness of 6 mm. The pressing time was 7 minutes for preheating at low pressure and 3 minutes for compression molding at high pressure.

[0060] Table 2: Recipe ingredients for the production of soft PVC.

[0061] The production of soft PVC was successful with all phosphoric acid ester preparations according to the invention. All samples were easy to process. Determination of flame retardancy, plasticizing effect, and volatility

[0062] The Limiting Oxygen Index (LOI) was used to assess flame retardancy. The LOI is a measure of the fire behavior of plastics and other materials. The LOI is the minimum oxygen concentration of a nitrogen / oxygen mixture at which combustion of a test specimen can just occur under standardized conditions. The test was conducted according to ISO 4589-2.

[0063] The plasticizing effect of the phosphoric acid esters was determined by measuring the Shore A hardness of the phosphoric acid ester-containing soft PVC compounds. The measurement principle is based on the penetration depth of a metal test pin into the material sample for 15 seconds with a force of 12.5 N. The Shore A hardness was determined using test specimens measuring 50 x 40 x 6 mm. The Shore hardness measurement was carried out in accordance with DIN ISO 7619-1. A Shore A hardness of less than 95 is considered an indicator of a plasticizing effect.

[0064] The volatility of the plasticizer was determined using thermogravimetric analysis (TGA) on a Mettler Toledo TGA / DSC 3+ instrument. The mass change was determined by evaporating a sample as a function of temperature and time. The individual samples (< 20 mg) were weighed into an open porcelain crucible and heated from room temperature to 500°C at a constant heating rate of 10 K / min under nitrogen. The mass loss of the individual products was determined at 245°C.

[0065] The results of the measurements are summarized in Table 3.

[0066] Table 3: Determination of the flame retardancy of the PVC samples produced and the

[0067] Volatility of the flame retardants used. The results surprisingly show that the phosphoric acid ester preparations according to the invention have a significantly lower volatility than the comparative example Disflamoll® DPO.

Claims

Patent claims 1. Mixtures containing: a) 0 to 30 wt.% (RO)3P=O, b) 10 to 90 wt.% (RO)2(PhO)P=O, c) 10 to 90 wt.% (RO)(PhO)2P=O and d) 0 to 0.5 wt.% (PhO)3P=O, each based on the total weight of components a) to d), wherein R represents the residue and Ph corresponds to the phenyl residue.

2. Mixtures according to claim 1, which contain less than 0.2% by weight of triphenyl phosphate, preferably less than 0.1% by weight of triphenyl phosphate.

3. Mixtures according to one or more of claims 1 or 2, which are present at 23°C and 1013 mbar as solids or as liquids, preferably as liquids having a dynamic viscosity of 20 to 5000 mPa s, particularly preferably of 50 to 2000 mPa s (each at 23°C).

4. Mixtures according to claim 3, which have a melting or softening point of below 70°C, preferably below 55°C, particularly preferably below 40°C.

5. A process for the preparation of mixtures according to one or more of claims 1 to 4 comprising the steps: (a) providing a mixture containing phosphorus oxychloride and phenoxyethanol, (b) reacting at least part of the mixture of a) at temperatures between 0°C and 50°C with separation of hydrogen chloride, (c) providing a mixture containing phenol and a base and optionally a solvent, (d) combining the mixture obtained from b) and the mixture from c) and reacting at temperatures between -20°C and 50°C to form a chloride salt.

6. The process according to claim 5, wherein a trialkylamine, preferably triethylamine, is used as the base in step c) 7. The process according to claim 5 or 6, wherein between step b) and step c) a distillative separation of reactants of step a) and / or by-products takes place.

8. Process according to one or more of claims 5 to 7, wherein after step d) a separation of reactants and / or by-products of steps b) and / or d) takes place, preferably by means of filtration, extraction, washing and / or distillation.

9. Use of mixtures according to one or more of claims 1 to 4 as flame retardants, preferably as flame retardants for synthetic polymers, materials of plant origin or materials of animal origin.

10. Use according to claim 9 as a flame retardant for polyvinyl chloride (PVC).

11. Molding composition comprising a mixture according to one or more of claims 1 to 4 and polyvinyl chloride (PVC).

12. Moulding composition according to claim 11, which contains from 5 to 150 parts by weight, preferably from 30 to 70 parts by weight of the phosphoric acid esters a) to d) based on 100 parts by weight of PVC.

13. Use of molding compositions according to claim 9 or 10 for the production of coatings, films, cables, pipelines, hoses, seals, conveyor belts, roofing membranes, adhesive tape films, tarpaulins, awnings or tents.

14. Use of mixtures according to one or more of claims 1 to 4 as hydraulic fluid.

15. Use of mixtures according to one or more of claims 1 to 4 as lubricant additive.

16. Use of mixtures according to one or more of claims 1 to 4 as an additive for paints, adhesives, sealants or coatings.

17. Use of a mixture according to one or more of claims 1 to 4 as a heat transfer medium.

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