Flame-retardant molding compositions with high cold flexibility

Abstract

The present invention relates to new flame-retardant thermoplastic molding compositions containing specific phenylphosphonic acid dialkyl esters which are characterized by good flame retardant properties and high cold flexibility.

Description

[0001] Flame-retardant molding compounds with high cold flexibility

[0002] Phosphoric acid esters are widespread and versatile industrial products used in various applications. For example, they are components or additives in plastics, hydraulic fluids, lubricants, heat transfer fluids, paints, adhesives, sealants, and coatings. However, doubts have been growing for some time as to whether these substances still meet current product safety requirements. Therefore, especially in consumer applications, there is an increasing demand for alternatives based on different chemical structures.

[0003] In plastics, established phosphoric acid esters are used as plasticizers and flame retardants. For example, they are used to produce flame-retardant flexible PVC for tarpaulins, floor coverings, seals, hoses, and cables. It is essential that the phosphorus compound used exhibits both plasticizing and flame-retardant properties in PVC. For technically demanding outdoor applications of flame-retardant flexible PVC, particularly high demands are placed on the cold flexibility of the workpiece to ensure that the desired plasticizing effect is maintained even at low ambient temperatures. The market also requires products with a low color number, as colored products require extensive color correction.

[0004] In the prior art, phosphoric acid esters are frequently used for such requirements. Those skilled in the art use mixed phosphoric acid alkyl aryl esters for this purpose (see, e.g., H. Bender et al., Manual for the Rubber Industry, Vol. 2, Leverkusen, Bayer AG, 1993, p. 492). An example is the phosphoric acid diphenyl(2-ethylhexyl) ester known from EP 0000240 A1, which is marketed as Disflamoll® DPO.

[0005] In addition to classic phosphoric acid esters, phenylphosphonic acid dialkyl esters are also known to experts as flame retardants and / or plasticizers in PVC. For example, phenylphosphonic acid dialkyl esters with a halogenated C2 or C3 alkyl chain are used as plasticizing flame retardants in PVC in CN 105601660 A, CN 105713039 A, and CN 10571340 A. However, the use of halogenated flame retardants is no longer accepted by the market after numerous brominated and chlorine-containing flame retardants, such as brominated diphenyl ethers or tris(chloroethyl)phosphate, had to be withdrawn from the market in many countries due to significant toxic effects on humans and the environment. A further disadvantage of the products described therein is their yellow color, which is undesirable for color-sensitive applications.

[0006] Halogen-free derivatives are known from US 2,400,577 A. This patent describes the preparation of phenylphosphonic acid dialkyl esters with a C4 to C8 alkyl chain and their suitability for use as plasticizers, among other things, without providing details about the plasticized polymer or its properties. In particular, neither its use in PVC nor the resulting properties, such as low-temperature flexibility or flame retardancy, are disclosed.

[0007] To overcome the aforementioned disadvantages of the prior art, halogen-free phenylphosphonic acid dialkyl esters with low color number are desirable, which exhibit good flame-retardant properties in thermoplastic molding compounds, especially in PVC, while simultaneously providing good plasticizing properties and high cold flexibility.

[0008] The object of the present invention was therefore to provide flame-retardant thermoplastic molding compounds, in particular flexible PVC, wherein both the flame-retardant effect and the plasticizing effect were to be achieved by halogen-free phenylphosphonic dialkyl esters with a low color number. The molding compounds were to exhibit high cold flexibility.

[0009] The problem is solved by thermoplastic molding compounds, preferably containing PVC, containing at least one phenylphosphonic acid dialkyl ester of the general formula (I)

[0010]

[0011] in which R 1 and R 2independently of one another, it represents a branched, unbranched, or cyclic C6-C12 alkyl, alkenyl, akinyl, or aralkyl group. An aralkyl group, to the person skilled in the art, is understood to be an alkyl group substituted with one or more aryl groups, such as a benzyl group. Surprisingly, it was found that phenylphosphonic acid dialkyl esters of general formula (I) exhibit high plasticizing and flame-retardant properties. Thermoplastic molding compounds produced with these also exhibit high cold flexibility.

[0012] The thermoplastic molding compounds according to the invention typically contain a) at least one thermoplastic (co)polymer

[0013] b) at least one phenylphosphonic acid dialkyl ester of general formula (I) c) optionally further excipients.

[0014] In a preferred embodiment, R 1 and R 2in formula (I) independently for n-hexyl, iso-hexyl, cyclohexyl, n-heptyl, iso-heptyl, n-octyl, 2-ethylhexyl, iso-octyl, n-nonyl, iso-nonyl, n-decyl, 2-propylheptyl, iso-decyl, n-dodecanyl, iso-dodecanyl. In a particularly preferred embodiment of the invention, R 1 and R 2 in formula (I) independently for 2-ethylhexyl, n-octyl, 2-propylheptyl, n-decyl or iso-decyl.

[0015] In one embodiment of the invention, the residues R 1 and R 2 identical in formula (I). In an alternative embodiment, the remainders R 1 and R 2 be different from each other.

[0016] The PVC compounds according to the invention can contain one or more phenylphosphonic acid dialkyl esters of general formula (I). For example, the PVC compounds according to the invention can contain one, two, three or more phenylphosphonic acid dialkyl esters of general formula (I).

[0017] Preferably, the phenylphosphonic acid dialkyl esters contained in the thermoplastic molding compounds according to the invention have a low acid number, since high acid numbers can negatively affect the long-term stability of the plastic used, for example, PVC. Preferably, the phenylphosphonic acid dialkyl esters contained in the thermoplastic molding compounds according to the invention have an acid number of less than 5 mg KOH / g, more preferably less than 1 mg KOH / g, particularly preferably less than 0.3 mg KOH / g, and most preferably less than 0.1 mg KOH / g.

[0018] Preferably, the phenylphosphonic acid dialkyl esters contained in the thermoplastic molding compounds according to the invention have a low color number, since high color numbers lead to discolored PVC compounds. Preferably, the phenylphosphonic acid dialkyl esters contained in the thermoplastic molding compounds according to the invention have a Hazen color number of less than 100, preferably less than 60, and most preferably less than 30.

[0019] The phenylphosphonic acid dialkyl esters contained in the thermoplastic molding compounds according to the invention can be easily prepared using synthesis methods known from the literature. For example, the synthesis published in Chem. Pharm. Bull. 1986, 34, 3121-3129 is mentioned, in which a solution of the alcohol and pyridine is reacted with a solution of phenylphosphonic acid dichloride (PhP(O)Ch) in a solvent. Mixtures of phenylphosphonic acid dialkyl esters can be obtained analogously by using different alcohols or mixtures of alcohols.

[0020] The thermoplastic molding compounds according to the invention contain thermoplastic (co)polymer(s), preferably thermoplastic (co)polymer(s) selected from polyethylene, polypropylene, polyvinyl chloride (PVC), polystyrene, polycarbonate, polyurethane, polyethylene terephthalate, polybutylene terephthalate, polyamide, polyester, acrylonitrile butadiene styrene copolymer, styrene acrylonitrile copolymer, polymethyl methacrylate, polyetherketone, polyetheretherketone, polyphenylene sulfide, polysulfone, polyethersulfone, polyphenylsulfone, polyamide-imide, cellulose ester or polylactic acid, particularly preferably polyvinyl chloride.

[0021] The molding compound according to the invention typically contains 10 to 95 parts by weight, preferably 20 to 90 parts by weight, more preferably 30 to 85 parts by weight and most preferably 35 to 75 parts by weight of thermoplastic (co-)polymer based on the total mass.

[0022] The molding compounds according to the invention contain 5 to 150 parts by weight, preferably 10 to 120 parts by weight, preferably 20 to 100 parts by weight, particularly preferably 30 to 70 parts by weight of the phenylphosphonic acid esters according to the invention based on 100 parts by weight of thermoplastic (co-)polymer(s).

[0023] The term (co-)polymer(s) stands for one or more copolymers and / or polymers, preferably for one or more polymers.

[0024] Depending on the application, the thermoplastic molding compounds according to the invention may contain further additives. Examples of additives include plasticizers, plasticizing polymers, polymeric modifiers, stabilizers (e.g., thermostabilizers, light stabilizers, antioxidants), co-stabilizers (e.g., acid scavengers, 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, e.g., RD ​​Maier, M. Schiller, Handbuch Kunststoff-Additive [Handbook of Plastic Additives], 4th edition, Munich, Carl Hanser Verlag, 2016, pp. 513 ff).

[0025] Typical flame retardants or synergists that can be used together with the phenylphosphonic acid dialkyl esters according to formula (I) in plastics are:

[0026] mineral flame retardants, such as aluminium hydroxide (ATH), magnesium hydroxide, antimony trioxide (ATO), antimony pentoxide, calcium hydroxide, carbonates, zinc borates, stannates, molybdates or graphite,

[0027] Phosphorus-containing flame retardants, such as phosphates, phosphonates, phosphinates, or phosphine oxides,

[0028] Halogenated compounds such as bromine or chlorine compounds,

[0029] nitrogen-containing compounds, such as melamine derivatives, ammonium sulfate or ammonium phosphate, or

[0030] Natural flame retardants of animal or plant origin.

[0031] Typical plasticizers that can be used together with the phenylphosphonic acid dialkyl esters according to formula (I) in plastics are carboxylic acid esters, for example, esters of benzoic acid or diesters of adipic acid, sebacic acid, azelaic acid, phthalic acid, terephthalic acid, or 1,2-cyclohexanedicarboxylic acid, or polyesters of these diaacids. Other typical plasticizers are alkylsulfonic acid esters of phenol.

[0032] The thermoplastic molding compounds according to the invention have flame-retardant and low-temperature flexibility properties. A further object of the present invention is therefore the use of phenylphosphonic acid dialkyl esters according to formula (I) as flame retardants and / or for improving the low-temperature flexibility of thermoplastic molding compounds.

[0033] The thermoplastic molding compounds according to the invention are particularly preferably made of polyvinyl chloride (PVC), i.e., compositions containing PVC which are in the form of granules, powder, paste, plastisol, or organosol. Flexible PVC is particularly preferred in these PVC molding compounds according to the invention. The PVC molding compounds according to the invention can be produced by mixing and compounding PVC with at least one phenylphosphonic acid dialkyl ester of formula (I) and optionally further excipients, e.g., stabilizers, in a manner known per se (see, e.g., G. Becker, D. Braun, Kunststoff-Handbuch, Polyvinylchlorid, Vol. 2 / 2, Munich, Vienna, Carl Hanser Verlag, 1986, p. 829 ff.) or by dispersing it to a ready-to-use plastisol or organosol.

[0034] The PVC molding compound according to the invention preferably contains 5 to 150 parts by weight, preferably 10 to 120 parts by weight, preferably 20 to 100 parts by weight, and particularly preferably 30 to 70 parts by weight of the phenylphosphonic acid esters according to the invention, based on 100 parts by weight of PVC.

[0035] The molding compounds according to the invention are used in coatings, films, floor coverings, cables, pipes, hoses, seals, conveyor belts, roofing membranes, adhesive tape films, tarpaulins, awnings and tents.

[0036] The invention also relates to a method for producing coatings, films, floor coverings, cables, pipes, hoses, seals, conveyor belts, roofing membranes, adhesive tape films, tarpaulins, awnings or tents using the molding compounds according to the invention, preferably PVC molding compounds, as well as the objects obtainable thereby.

[0037] Furthermore, the invention relates to coatings, films, floor coverings, cables, pipes, hoses, seals, conveyor belts, roofing membranes, adhesive tape films, tarpaulins, awnings or tents containing the molding compounds according to the invention, preferably PVC molding compounds. Examples

[0038] Determining the Hazen color number

[0039] The Hazen color number was determined using a Hach Lico 690 Spectralcolori meter. The measurement was carried out according to DIN EN ISO 6271.

[0040] Determination of the acid number of phenylphosphonic acid dialkyl esters

[0041] The acid value 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 out, 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 manner, but without the sample.

[0042] Synthesis examples

[0043] General synthesis procedure for the preparation of phenylphosphonic acid dialkyl esters

[0044] Following the established procedure Chem. Pharm. Bull. 1986, 34, 3121-3129, a solution of the alcohol(s) and triethylamine in toluene is placed in a reactor equipped with a stirrer, internal thermometer, nitrogen inlet, and reflux condenser. Phenylphosphonic dichloride is added at 0-5 °C. After the addition of the alcohol(s), the reaction mixture is diluted with water. The organic phase is washed twice with sodium hydroxide solution (1 mol / L) and three times with water. The product is obtained after separation of the solvents by distillation.

[0045] Synthesis example 1: Phenylphosphonic acid di-n-butyl ester

[0046] Prepared from phenylphosphonic acid dichloride (1.00 parts by weight), n-butanol (0.80 parts by weight), triethylamine (1.20 parts by weight), and toluene (7.0 parts by weight). The acid value was <0.1 mg KOH / g. The Hazen color value was 10. Synthesis example 2: Phenylphosphonic acid bis(2-ethylhexyl) ester

[0047] Prepared from phenylphosphonic acid dichloride (1.00 parts by weight), 2-ethylhexanol (1.41 parts by weight), triethylamine (1.20 parts by weight), and toluene (7.0 parts by weight). The acid value was <0.1 mg KOH / g. The Hazen color value was 12.

[0048] Synthesis example 3: Phenylphosphonic acid bis(2-propylheptyl) ester

[0049] Prepared from phenylphosphonic acid dichloride (1.00 parts by weight), 2-propylheptanol (1.71 parts by weight), triethylamine (1.21 parts by weight), and toluene (7.0 parts by weight). The acid value was <0.1 mg KOH / g. The Hazen color value was 5.

[0050] Synthesis example 4: Phenylphosphonic acid diisodecyl ester

[0051] Produced from phenylphosphonic acid dichloride (1.00 parts by weight), isodecanol (Exxal® 10 from ExxonMobil; 1.71 parts by weight), triethylamine (1.21 parts by weight), and toluene (7.0 parts by weight). The acid value was <0.1 mg KOH / g. The Hazen color value was 11.

[0052] Comparison patterns of known phosphoric acid esters

[0053] Disflamoll® DPO from Lanxess Deutschland GmbH was used as a comparison sample. This is a phosphoric acid diphenyl(2-ethylhexyl) ester. The acid number of the sample used was <0.1 mg KOH / g. The hazen color number was 5.

[0054] Production of flexible PVC

[0055] The flexible PVC molding compounds used for testing were produced on a laboratory rolling mill. After adding the mixture of all formulation components (see Table 2), it was left on the roller until a film formed. From the point of film formation, the compounds were compounded for another 10 minutes on the rolling mill and finally removed as rolled film. The rolling temperature was 165°C.

[0056] The test specimens for determining the LOI were produced from the roller skins using a press. The pressing temperature was 170°C, the pressing time was 4 minutes for preheating at low pressure (< 10 bar) and 2 minutes at high pressure (> 100 bar). Test specimens with dimensions of 90 x 13 x 4 mm were sawn from the 4 mm thick press plates.

[0057] The test specimens used to determine the hardness of the compounds (50 x 40 x 6 mm) were pressed for a longer period 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 pressing at high pressure.

[0058] Table 1: Ingredients for the production of flexible PVC.

[0059] Component Function Description Quantity (parts by weight) A PVC Vinnol S4170 100

[0060] B Co-stabilizer EPO 65-1 2.5

[0061] epoxidized soybean oil

[0062] C PVC stabilizer Bärostab UBZ 780 RF 2.5

[0063] D Flame retardants As shown in Table 2 55

[0064]

[0065] PVC samples were produced according to this regulation.

[0066] Determination of flame retardancy

[0067] 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. It represents the minimum oxygen concentration in a nitrogen / oxygen mixture below which combustion of a test specimen can still occur under standardized conditions. The higher the LOI, the greater the effectiveness of the flame retardant. The test was conducted according to ISO 4589-2.

[0068] Determination of the plasticizer effect

[0069] The plasticizing effect of phosphoric acid esters was determined by measuring the Shore A hardness of phosphoric acid ester-containing soft PVC compounds. The measurement principle is based on the penetration depth of a metal probe into the material sample for 15 seconds with a force of 12.5 N. The Shore A hardness was determined for test specimens with dimensions of 50 x 40 x 6 mm. The Shore hardness measurement was performed in accordance with DIN ISO 7619-1.

[0070] Determination of cold flexibility

[0071] The low-temperature flexibility of PVC compounds was determined using the dynamic-mechanical method. In this method, a material sample is subjected to a time-varying sinusoidal force as a function of temperature, causing the sample to deform in phase. The force and deformation amplitudes, as well as the phase shift between the force and deformation signals, are measured on the sample. This allows the determination of the viscoelastic behavior (relaxation behavior, glass transition, mechanical moduli, damping behavior, softening, viscous flow, crystallization and melting, gelation, and other phase transitions) of materials. The glass transition temperature is particularly important for polymeric materials because it provides an indication of a material's low-temperature flexibility. The glass transition temperatures were determined using a Mettler Toledo DMA 1 instrument. The measuring range is between -80 °C and 70 °C. The heating rate is 2 K / min.The frequency is 1 Hz. The evaluation is carried out according to DIN 65583 (2% method).

[0072] The results of the measurements are summarized in Table 2.

[0073] Table 2: Determination of processability, flame retardancy, and cold flexibility of the manufactured PVC samples.

[0074] V1 V2 V3 V4 V5 Example (Comparison (invention (invention (comparative example) according to) according to) according to) example) Flame retardant Disflamoll S1 S2 S3 S4 (Component D) DPO Processability - + + + + LOI nb 28 28 28 29 Shore A nb 71 70 70 74 Glass transition nb.b. -61 -63 -62 -50 temperature

[0075]

[0076] nb = not determined.

[0077] The results show that the phenylphosphonic acid di-n-butyl ester S1 disclosed in US 2,400,577 A cannot be processed into PVC. Due to its high volatility, the compound evaporated during the rolling of the PVC compounds. No measurement data could be obtained for this material. In contrast, the phenylphosphonic acid bis(2-ethylhexyl) ester S2, the phenylphosphonic acid bis(2-propylheptyl) ester S3, and the phenylphosphonic acid diisodecyl ester S4 could be processed into PVC. The flame retardancy (LOI) and the plasticizing effect (Shore A hardness) of the produced PVC compounds V2-V4 are comparable to the PVC compound V5, which contains the prior art phosphoric acid diphenyl(2-ethylhexyl) ester (Disflamoll® DPO). Surprisingly, the cold flexibility of the PVC compounds V2-V4 according to the invention is significantly higher than that of V5, which can be seen from a lower value of the glass transition temperature of V2-V4 compared to V5.

Claims

Patent claims 1. Thermoplastic molding compounds containing thermoplastic (co-)polymer(s) and, based on 100 parts by weight of thermoplastic (co-)polymer(s), at least one phenylphosphonic acid dialkyl ester of general formula (I) 5 to 150 parts by weight OO— R w / O R in which R 1 and R 2 independently of each other stand for branched or unbranched or cyclic C6-C12 alkyl, alkenyl, akinyl or aralkyl residues.

2. Thermoplastic molding compounds according to claim 1, comprising (co-)polymer(s) of polyethylene, polypropylene, polyvinyl chloride, polystyrene, polyurethane, polyethylene terephthalate, polybutylene terephthalate, polyamide, polyester, acrylonitrile-butadiene-styrene copolymer, styrene-acrylonitrile copolymer, polymethyl methacrylate, polyetherketone, polyetheretherketone, polyphenylene sulfide, polysulfone, polyethersulfone, polyphenylsulfone, polyamide-imide, cellulose ester or polylactic acid, preferably polyvinyl chloride.

3. Thermoplastic molding compounds according to claim 1, comprising (co-)polymer(s) of polyvinyl chloride (PVC).

4. Thermoplastic molding compounds according to one or more of claims 1 to 3, characterized in that R 1 and R 2in formula (I) independently represents n-hexyl, iso-hexyl, cyclohexyl, n-heptyl, iso-heptyl, n-octyl, 2-ethylhexyl, iso-octyl, n-nonyl, iso-nonyl, n-decyl, 2-propylheptyl, iso-decyl, n-dodecanyl, iso-dodecanyl, most preferably 2-ethylhexyl, n-octyl, 2-propylheptyl, n-decyl or iso-decyl.

5. Thermoplastic molding compounds according to one or more of claims 2-4 comprising 10 to 95 parts by weight, preferably 20 to 90 parts by weight, more preferably 30 to 85 parts by weight and most preferably 35 to 75 parts by weight of the thermoplastic (co-)polymer(s) based on the total mass.

6. Thermoplastic molding compounds according to one or more of claims 1-5, comprising 10 to 120 parts by weight, preferably 20 to 100 parts by weight, particularly preferably 30 to 70 parts by weight of phenylphosphonic acid dialkyl esters of formula (I) based on 100 parts by weight of the thermoplastic (co-)polymer(s).

7. Thermoplastic molding compounds according to one or more of claims 1-5, comprising PVC and 10 to 120 parts by weight, preferably 20 to 100 parts by weight, particularly preferably 30 to 70 parts by weight of phenylphosphonic acid dialkyl esters of formula (I) based on 100 parts by weight of PVC.

8. Use of thermoplastic molding compounds according to one or more of claims 1 to 6 for the production of coatings, films, floor coverings, cables, pipes, hoses, seals, conveyor belts, roofing membranes, adhesive tape films, tarpaulins, awnings or tents.

9. Method for producing coatings, films, floor coverings, cables, pipes, hoses, seals, conveyor belts, roofing membranes, adhesive tape films, tarpaulins, awnings or tents, wherein molding compounds according to one or more of claims 1 to 7 are used.

10. Coatings, films, floor coverings, cables, pipes, hoses, seals, conveyor belts, roofing membranes, adhesive tape films, tarpaulins, awnings or tents containing molding compounds according to one or more of claims 1 to 7 or obtainable by the method according to claim 9.

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