Phosphate ester composition for flame-retardant soft PVC with low volatility

Abstract

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

Description

[0001] Phosphates can be used in various technical applications, for example 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).

[0002] The flame-retardant effect of phosphates has been demonstrated in various plastics, for example in PVC (cf. GB 2 302 543 A), polyolefins (cf. US 11,008,440 B2), cellulose esters (US 9,000,148 B2), polyurethanes (cf. US 8,129,457 B2) or styrene polymers (cf. US 8,026,303 B2).

[0003] Phosphates are of particular importance in the processing of soft PVC, where they act both as flame retardants and plasticizers. Mixed phosphoric acid alkyl aryl esters are often used here. One example is phosphoric acid 2-ethylhexyl-diphenyl ester, which is known from EP 0 000 240 A1, as a DPO is marketed.

[0004] However, compared to phosphoric acid triaryl esters, mixed phosphoric acid alkyl aryl esters have the disadvantage that they have a lower flame-retardant effect and are more volatile. The latter leads to a loss of plasticizer and thus to an undesired gradual embrittlement of the soft PVC article over its service life.

[0005] Furthermore, the phosphoric acid alkyl aryl esters from the prior art, such as DPO, contain 1 to 5% by weight of phosphoric acid triphenyl ester. Its hazardous substance properties lead to a demand for a continuous reduction of this substance content in consumer applications.

[0006] There is therefore no lack of attempts to find improved phosphoric acid alkyl aryl esters. By way of example, phosphates based on 2-phenoxyethanol and phenol are known from R. T. Gottesman et al., Fire Retardants, Proc. Int. Symp. Flammability Fire Retardants 1976, 225-237. These products are described as phosphate ester compositions, but neither their composition nor their amount ratios are disclosed. There is also no information about the phosphoric acid triphenyl ester content or the volatility of the products.

[0007] When the preparation of the phosphates based on 2-phenoxyethanol and phenol according to Gottesman et al. was reworked, it was found that a high content of phosphoric acid triphenyl ester occurs and the volatility needs to be improved.

[0008] It is therefore the object of the present invention to provide a mixture which is characterized by low volatility and low content of triphenyl phosphate and which achieves a high flame- retarding effect, in particular in compositions with PVC molding compounds. Preferably, this mixture should have a low melting point and ideally be present in liquid form at room temperature, which facilitates processing. Preferably, this mixture should also be obtainable by less complex methods and with a low content of triphenyl phosphate. Furthermore, a plasticizing effect should be achieved in PVC.

[0009] This object is achieved by a mixture comprising the following items:

[0010] a) 0 to 30 % by weight of (RO)3P=0,

[0011] b) 10 to 90 % by weight of (RO)2(PhO)P=0,

[0012] c) 10 to 90 % by weight of (RO)(PhO)2P=0, and

[0013] d) 0 to 0.5 % by weight of (PhO)3P=0

[0014] these items 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,

[0015] where R is a radical

[0016]

[0017] and Ph corresponds to a phenyl group.

[0018] In a preferred embodiment of the present invention, the mixture comprises the following items:

[0019] a) 1 to 30 % by weight of (RO)3P=0,

[0020] b) 20 to 84 % by weight of (RO)2(PhO)P=0,

[0021] c) 15 to 79 % by weight of (RO)(PhO)2P=0, and

[0022] d) 0 to 0.5 % by weight of (PhO)3P=0

[0023] these items 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.

[0024] In a further preferred embodiment of the present invention, the mixture comprises the following items:

[0025] a) 5 to 30 % by weight of (RO)3P=0,

[0026] b) 20 to 80 % by weight of (RO)2(PhO)P=0,

[0027] c) 15 to 75 % by weight of (RO)(PhO)2P=0, and

[0028] d) 0 to 0.2 % by weight of (PhO)3P=0

[0029] These amounts are 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.

[0030] In a further preferred embodiment of the application, the mixture comprises the following:

[0031] a) 10 to 25 % by weight of (RO)3P=0,

[0032] b) 50 to 75 % by weight of (RO)2(PhO)P=0,

[0033] c) 15 to 40 % by weight of (RO)(PhO)2P=0, and

[0034] d) 0 to 0.2 % by weight of (PhO)3P=0

[0035] These amounts are 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.

[0036] In a particularly preferred embodiment of the application, the phosphate ester composition according to the application comprises less than 0.2 % by weight of triphenyl phosphate, particularly preferably less than 0.1 % by weight of triphenyl phosphate.

[0037] Preferably, the mixture according to the application is present as a solid or as a liquid at 23 °C and 1013 mbar, particularly preferably as a liquid having a dynamic viscosity of 20 to 5000 mPa-s, most preferably 50 to 2000 mPa-s (in each case at 23 °C).

[0038] Preferably, the mixture according to the application has a melting point or softening point below 70 °C, preferably below 55 °C, particularly preferably below 40 °C.

[0039] Preferably, the mixture according to the application has an acid value 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.

[0040] It has surprisingly been found that PVC molding compounds comprising the mixture according to the present application have a high flame retardancy. The mixture according to the present application can surprisingly easily be prepared in a novel way in such a way that the mixture contains no or only very little triphenyl phosphate.

[0041] The present application further provides a process for preparing the mixture according to the present application, the process comprising the following steps:

[0042] (a) providing a mixture comprising phosphorus oxychloride and phenoxyethanol,

[0043] (b) reacting at least a portion of the mixture from a) at a temperature between 0 °C and 50 °C to remove hydrogen chloride,

[0044] (c) providing a mixture comprising phenol and a base and optionally a solvent,

[0045] (d) combining the mixture obtained from b) and the mixture from c) and reacting it at a temperature between -20 °C and 50 °C to form a chloride salt.

[0046] In alternative embodiments, at least a portion of the phosphorus oxychloride is metered in step b) only. It is also possible that at least a portion of the phenoxyethanol is metered in step b) only.

[0047] The reaction according to step b) is typically carried out in the range of 0 °C to 50 °C, preferably in the range of 10 °C to 40 °C, particularly preferably in the range of 20 °C to 30 °C.

[0048] Optionally, a distillative removal of (unreacted) reactants from step a) and / or of formed by-products, such as hydrogen chloride, can be carried out between step b) and step c). The distillation can be carried out as a batch process or as a continuous process. The temperature of the distillation is preferably in the range of 0 °C to 50 °C. Particularly preferably, the distillation is carried out at the reaction temperature of step b) or at a temperature between 0 °C and the reaction temperature of step b). The distillation is carried out in the pressure range of 0.01 mbar to 1013 mbar, preferably in the range of 0.01 mbar to 100 mbar, very particularly preferably in the range of 0.01 mbar to 50 mbar.

[0049] All commercially available bases known to the person skilled in the art can be used as the base of step c). These include alkali metal hydroxides such as NaOH, KOH or LiOH, or amines such as triethylamine, imidazole, 1-methylimidazole, diisopropylethylamine, dibutylamine, morpholine and the like, including ammonia solutions or ammonia-containing solutions.

[0050] In preferred embodiments, 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 solvents. These include, for example, water, aromatic hydrocarbons such as toluene, xylene, aliphatic hydrocarbons such as pentane, hexane, cyclohexane, heptane or long-chain hydrocarbons, or chlorinated hydrocarbons such as dichloromethane, dichloroethane or chlorobenzene.

[0051] In alternative embodiments, at least a portion of the mixture provided in step c) is metered into the mixture obtained in step b). It is also possible to meter in at least a portion of the base or a portion of the phenol only in step d).

[0052] 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.

[0053] The removal of the reactants and / or of the by-products from steps b) and / or d) can be carried out after step d) by filtration, extraction, washing and / or distillation. In preferred embodiments of the application, the chloride salts formed as by-products are first removed. If water is used as optional solvent in step c), the removal can be carried out by simply separating the aqueous and the organic phase. If step c) is carried out without water, the chloride salts can be removed by filtration.

[0054] For further purification, the product can be subjected to a washing. Suitable washing solutions are, for example, sodium hydroxide solution or potassium hydroxide solution or water. The washing is usually carried out at a temperature between 20°C and 50°C.

[0055] The solvent optionally used in step c) can be removed by distillation. The conditions for the distillation can be easily determined by the person skilled in the art.

[0056] Depending on the application, the mixture according to the application can also comprise further auxiliaries. Examples of suitable auxiliaries are plasticizers, plasticized polymers, polymer modifiers, stabilizers (for example heat stabilizers, light stabilizers, antioxidants), co-stabilizers (for example acid scavengers, radical scavengers), internal and external lubricants, viscosity regulators, fillers, colored pigments, dyes, flame retardants, flame retardant synergists, blowing agents and further functional additives (such as antistatic agents, nucleating agents, UV protection agents or biocides) (see for example R.D. Maier, M. Schiller, Handbuch Kunststoff-Additive [Plastics Additives Handbook], 4th edition, Munich, Carl Hanser Verlag, 2016, page 513 ff.).

[0057] The mixtures according to the application are suitable as flame retardants. Thus, the present application further provides the use of the mixtures according to the application as flame retardants.

[0058] The mixtures according to the application can be used as flame retardants in all applications of flame retardants known to the person skilled in the art. Preferably, the mixtures according to the application are used as flame retardants for:

[0059] - synthetic polymers, such as polyolefins, polyvinyl chloride, polycarbonates, styrene-based (co)polymers, polyamides, polyesters, polyurethanes, elastomers (such as NBR, CR, SBR or EPDM) and thermosetting resins (such as epoxy resins, unsaturated polyester resins and phenol formaldehyde resins),

[0060] - materials of vegetable origin, such as wood, wood-plastic composites, paper and cardboard, and

[0061] - materials of animal origin, such as leather.

[0062] It is particularly preferred to use the mixtures according to the application as flame retardants for polyvinyl chloride (PVC), for example in PVC molding compounds (i.e. compositions comprising PVC in the form of granules, powders, pastes or plastisols).

[0063] The present application therefore also provides compositions, preferably in the form of granules, powders, pastes or plastisols, which comprise the mixtures according to the application and polyvinyl chloride (PVC). These PVC molding compounds according to the application are preferably soft PVC. The PVC molding compounds according to the application can be produced by mixing and compounding or dispersing PVC with the mixtures according to the application and optionally further auxiliaries (for example stabilizers) in a known manner (see, for example, G. Becker, D. Braun, Kunststoff-Handbuch, Polyvinylchlorid [Plastics Handbook, Polyvinyl Chloride], Volume 2 / 2, Munich, Vienna, Carl Hanser Verlag, 1986, page 829 ff.) to form a processable plastisol or organosol.

[0064] The PVC molding compound according to the application preferably comprises 5 to 150 parts by weight, particularly preferably 30 to 70 parts by weight, of the phosphoric ester according to the application (such as (RO)3P=0, (RO)2(PhO)P=0, (RO)(PhO)2P=0 and (PhO)3P=0 as defined above) based on 100 parts by weight of PVC. In a preferred embodiment, the PVC molding compound according to the application comprises 5 to 150 parts by weight, particularly preferably 30 to 70 parts by weight, of the phosphoric ester according to the application based on 100 parts by weight of PVC.

[0065] The PVC molding compound according to the application can be used in coatings, films, cables, pipes, hoses, seals, conveyor belts, roof membranes, tape membranes, tarpaulins, awnings and tents.

[0066] The application further provides the use of the mixture according to the application in hydraulic fluids or for the production of hydraulic fluids. Preferably, the mixture according to the application is used in flame-retardant hydraulic fluids.

[0067] The application further provides the use of the mixture according to the application as a lubricant additive. Preferably, the mixture according to the application is used in flame-retardant lubricants.

[0068] The application further provides the use of the mixture according to the application as an additive for paints, adhesives, sealants and coatings.

[0069] The application further provides the use of the mixture according to the application as a heat transfer medium or in formulations for use as a heat transfer medium. Preferably, the mixture according to the application is used as a heat transfer medium or in a heat transfer medium formulation in the immersion cooling of electrical components. In addition to the mixture according to the application, the heat transfer medium formulation comprises, for example, further trialkyl phosphates, triaryl phosphates, mineral oils, polyalphaolefins, esters, antioxidants, metal deactivators, flow additives, corrosion inhibitors, foam inhibitors, demulsifiers and / or pour point depressants.

[0070] Example

[0071] Determination of the composition of the phosphoric ester composition

[0072] Quantitative GC-FID analysis was performed using an Agilent 7890A GC instrument equipped with a CB-Sil 5CB quartz capillary column (length: 30 m, diameter: 0.32 mm, film thickness: 3.00 pm). The carrier gas used was hydrogen. The samples (dissolved in acetone) were injected in split mode (86: 1) at a temperature of 300 °C. The following temperature program was set: starting temperature of 60 °C; temperature of 150 °C with a heating rate of 10 °C / min; then a heating rate of 25 °C / min to a temperature of 280 °C, hold time: 10 min; then a heating rate of 25 °C / min to a final temperature of 320 °C / min, hold time: 10 min. The evaluation was performed by integration of the corresponding baseline-separated signals and conversion of the peak areas to contents after previous calibration.

[0073] Determination of the viscosity of the phosphate ester composition

[0074] The dynamic viscosity of the phosphate ester was measured according to DIN 53018 using an Anton Paar MCR 102 shear rheometer at a shear rate of 200 s -1 at the specified temperature.

[0075] Determination of the acid value of the phosphate ester composition

[0076] The acid value of the sample was determined according to DIN EN ISO 2114 (method B, colorimetric titration with phenothalin). For this purpose, the sample (10 g) was weighed out, dissolved in acetone (200 ml) and water (50 ml) and mixed with 2-3 drops of a phenothalin solution (0.1 % by weight in ethanol / water (v / v = 4 / 1). The sodium hydroxide solution (0.1 mol / 1) was titrated with a burette under stirring until the color changed from colorless to pink for at least 10 seconds. The blank value was measured in the same way, but without sample.

[0077] Synthesis Example

[0078] Comparative Example 1 (V1)

[0079] Preparation according to R. T. Gottesman et al., Fire Retardants, Proc. Int. Symp. Flammability Fire Retardants 1976, 225-237:

[0080] Phosphorus oxychloride (200 parts by weight) was first charged into a reactor with stirrer, internal thermometer, nitrogen inlet and reflux condenser. Phenol (245 parts by weight) and water (600 parts by weight) were added. The reaction product thus obtained was reacted with sodium hydroxide (129 parts by weight) to yield a two-phase reaction mixture. After separation of the phases, the organic phase was washed with a sodium hydroxide solution (0.5 mol / 1; 500 parts by weight) and then with water (500 parts by weight). The 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 value was 0.1 mg KOH / g. The phosphate ester composition was 0.5% by weight of (phenoxyethyl O)3P=0, 13.7% by weight of (phenoxyethyl O)2(PhO)P=0, 84.8% by weight of (phenoxyethyl O)(PhO)2P=0 and 1.0% by weight of (PhO)3P=0 ("TPP").

[0081] Synthesis Example 1 (S1 ) according to the application

[0082] Phosphorus oxychloride (200 parts by weight) was first charged into a reactor with stirrer, internal thermometer, nitrogen inlet and reflux condenser. Phenol (245 parts by weight) and water (600 parts by weight) were added. The reaction product thus obtained was reacted with sodium hydroxide (129 parts by weight) to yield a two-phase reaction mixture. After separation of the phases, the organic phase was washed with a sodium hydroxide solution (0.5 mol / 1; 500 parts by weight) and then with water (500 parts by weight). The 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 value was 0.1 mg KOH / g. The phosphate ester composition was 0.5% by weight of (phenoxyethyl O)3P=0, 13.7% by weight of (phenoxyethyl O)2(PhO)P=0, 84.8% by weight of (phenoxyethyl O)(PhO)2P=0 and 1.0% by weight of (PhO)3P=0 ("TPP").

[0083] Synthesis Example 2 (S2) according to the application

[0084] First, phosphorus oxychloride (201 parts by weight) was charged into a reactor with stirrer, internal thermometer, nitrogen inlet and reflux condenser. Phenoxyethanol (361 parts by weight) was metered in such a way that the internal temperature was kept 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 kept under the final conditions for 1 h. The reaction mixture was metered into a mixture of dichloromethane (401 parts by weight), phenol (186 parts by weight) and triethylamine (222 parts by weight) at 0°C, where the internal temperature was kept between 0°C and 15°C. The solids were 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 value was <0.1 mg KOH / g. The product mixture contained 20.8% by weight of (phenoxyethyl O)3P=O, 58.9% by weight of (phenoxyethyl O)2(PhO)P=O, 20.3% by weight of (phenoxyethyl O)(PhO)2P=O and <0.1% by weight of (PhO)3P=O ("TPP").

[0085] Table 1 : Amounts used and analytical data for the synthesis of examples V1, S1 and S2.

[0086]

[0087] Production of soft PVC

[0088] The soft PVC molding compounds for testing were produced on a laboratory roll mill. After the mixture of all formulation ingredients (see Table 2) was added, it was left on the rolls until a sheet had formed. From the point in time when the sheet had formed, the compounds were mixed on the roll mill for a further 10 minutes and finally removed as a rolled sheet. The rolling temperature was 165°C.

[0089] The test specimens for determining the LOI were produced from the rolled sheet using a press. The pressing temperature was 170°C; the pressing duration under low pressure (<10 bar) preheated was 4 minutes and under high pressure (>100 bar) was 2 minutes. From the 4 mm thick pressed plate, test specimens of dimensions 90 x 13 x 4 mm were sawn out.

[0090] Due to the large thickness of 6 mm, the test specimens for determining the hardness of the compounds (50 x 40 x 6 mm) were pressed for longer at the same temperature. The pressing duration under low pressure preheated was 7 minutes and under high pressure compression molded was 3 minutes.

[0091] Table 2: Formulation ingredients for producing soft PVC.

[0092]

[0093] Soft PVC was successfully produced with all phosphate ester formulations according to the present application. All samples were easily processable.

[0094] Determination of flame retardancy, plasticizing effect and volatility

[0095] The flame retardancy was assessed using the limiting oxygen index (= LOI). The LOI is a measure of the flammability behavior of plastics and other materials. The LOI is the lowest oxygen concentration of a nitrogen / oxygen mixture with which a test specimen just can burn under standardized conditions. The test was performed according to ISO 4589-2.

[0096] The plasticizing effect of the phosphates of the soft PVC compounds containing phosphates was determined using the Shore A hardness measurement. The measurement principle is based on the penetration depth of a metal test pin into a material sample under a force of 12.5 N for 15 s. The Shore A hardness of test specimens with dimensions of 50 x 40 x 6 mm was determined. The Shore hardness measurement was performed according to DIN ISO 7619-1. A Shore A hardness of less than 95 was considered as an indicator for the plasticizing effect.

[0097] The volatility of the plasticizers was determined by thermogravimetric analysis (TGA) on a TGA / DSC 3+ instrument of the Mettler Toledo group. Here, the mass change was determined by evaporation of the sample depending on temperature and time. The individual samples (< 20 mg) were weighed in an open porcelain crucible and heated from room temperature to 500 °C under nitrogen with a constant heating rate of 10 K / min. The mass loss of the individual products was determined at 245 °C.

[0098] The results of the measurements are compiled in Table 3.

[0099] Table 3: Determination of flame retardancy of the produced PVC test specimens and volatility of the flame retardants used therefor.

[0100]

[0101] These results surprisingly show that the phosphate ester formulations according to the present application have a significantly lower volatility than the comparative examples DPO.

Claims

1. A mixture comprising the following items: a) 0 to 30 % by weight of (RO)3P=0, b) 10 to 90 % by weight of (RO)2(PhO)P=0, c) 10 to 90 % by weight of (RO)(PhO)2P=0, and d) 0 to 0.5 % by weight of (PhO)3P=0 these items in each case based on the total weight of components a) to d), wherein R is a group and Ph corresponds to phenyl.

2. The mixture according to claim 1 comprising less than 0.2 % by weight of triphenylphosphite, preferably less than 0.1 % by weight of triphenylphosphite.

3. The mixture according to one or both of claims 1 and 2 which is present as a solid or as a liquid at 23 °C and 1013 mbar, preferably as a liquid having a dynamic viscosity of 20 to 5000 mPa-s, particularly preferably 50 to 2000 mPa-s (in each case at 23 °C).

4. The mixture according to claim 3 which has a melting or softening point below 70 °C, preferably below 55 °C, particularly preferably below 40 °C.

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

6. The method of claim 5, wherein, The base used in step c) is a trialkylamine, preferably triethylamine.

7. The method of claim 5 or 6, wherein, Distillative removal of reactants from step a), and / or of by-products is carried out between steps b) and c).

8. The method according to one or more of claims 5 to 7, wherein, Removal of reactants and / or of by-products from step b) and / or d) is carried out after step d), preferably by filtration, extraction, washing and / or distillation.

9. Use of the mixture according to one or more of claims 1 to 4 as a flame retardant, preferably as a flame retardant for synthetic polymers, materials of vegetable origin or materials of animal origin.

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

11. A molding compound comprising the mixture according to one or more of claims 1 to 4 and polyvinyl chloride (PVC).

12. The molding compound according to claim 11 comprising 5 to 150 parts by weight, preferably 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 the molding compound according to claim 9 or 10 for the production of coatings, films, cables, pipes, hoses, seals, conveyor belts, roof membranes, tape membranes, tarpaulins, awnings or tents.

14. Use of the mixture according to one or more of claims 1 to 4 as a hydraulic fluid.

15. Use of the mixture according to one or more of claims 1 to 4 as additive for lubricants.

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

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

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