Flame-retardant thermoplastic molding compositions

Abstract

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

Description

[0001] Flame-retardant thermoplastic molding compounds

[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 floor coverings, seals, hoses, or cables. It is essential that the phosphorus compound used exhibits both plasticizing and flame-retardant properties in PVC.

[0004] Besides the classic phosphoric acid esters, phenylphosphonic acid diaryl esters are also known to experts as flame retardants in various plastics. For example, phenylphosphonic acid bis(2,6-dimethylphenyl) ester has been used in ABS polymers (J. Macromol. Sei., Part B 2012, 51, 2141-2156) and in epoxy resins (J.

[0005] Appl. Polym. Sei. 2015, 132, 42765). Phenylphosphonic acid bis(4-tert-butylphenyl) ester has been used in polycarbonates (US 2009 149587 A1). The use of phenylphosphonic acid diphenyl ester as a flame retardant and plasticizer is mentioned in EP 0043482 A2, without providing details or test results.

[0006] CN 116396573 A describes phenylphosphonic acid diaryl esters as plasticizing flame retardants in PVC. Cardanol is used as a raw material for the production of these products and is reacted with phenylphosphonic acid dichloride to form a mixture of phenylphosphonic acid diaryl esters. The plasticizing effect of these products is attributed to the C15 side chain of cardanol. Due to the associated high molar mass of cardanol, the products described therein have a very low phosphorus content of less than 4.5 wt%. In practice, such a low phosphorus content means that further flame-retardant additives must be added to achieve the desired flame-retardant effect in addition to the plasticizing effect. Therefore, when testing the phosphonates according to the invention, the inventors exclusively use formulations containing other flame retardants, such as montmorillonite, anhydrite, and chlorinated polyethylene.This complex formulation represents a considerable additional technical effort. Furthermore, mineral flame retardants negatively affect the transparency of the PVC compound, which is undesirable for some demanding applications. The publication does not address the compatibility and storage stability of the phenylphosphonic acid diaryl esters used with PVC. Another disadvantage of the invention is that Cardanol is currently not available on the market in technically relevant quantities. Moreover, based on the amounts of plasticizer used, the high tensile strength, and the low elongation at break of the resulting PVC, it is obvious to those skilled in the art that D2 does not refer to flexible PVC but rigid PVC.

[0007] To overcome the aforementioned disadvantages of the prior art, phenylphosphonic acid diaryls are desirable, which exhibit good flame-retardant properties in thermoplastic molding compounds, especially in PVC, while simultaneously providing good plasticizing properties.

[0008] The object of the present invention was therefore to provide flame-retardant and plasticized thermoplastic molding compounds, in particular flexible PVC, whereby both the flame-retardant and plasticizing effects were to be achieved by means of phenylphosphonic acid diaryl esters. For the technical applicability of plasticizing flame retardants, it is necessary that the additive be compatible with the respective plastic. A further object of the invention was therefore to provide phenylphosphonic acid diaryl esters that are compatible with thermoplastics, in particular PVC.

[0009] The problem is solved by thermoplastic molding compounds, preferably PVC-containing molding compounds, containing at least one thermoplastic (co)-polymer and at least one phenylphosphonic acid diaryl ester of general formula (I)

[0010]

[0011] in which Ar 1 for a singly or multiply alkyl-substituted aryl group with a total of 7-10 carbon atoms and Ar 2 for phenyl, 2-methylphenyl, 3-methylphenyl or 4-methylphenyl. The thermoplastic molding compounds according to the invention typically contain

[0012] a) at least one thermoplastic (co)polymer

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

[0014] In a preferred embodiment, Ar 1in formula (I) for 2-methylphenyl, 3-methylphenyl, 4-methylphenyl, 2-ethylphenyl, 3-ethylphenyl, 4-ethylphenyl, 2-propylphenyl, 3-propylphenyl, 4-propylphenyl (where "propylphenyl" means both n-propylphenyl and isopropylphenyl), 2-butylphenyl, 3-butylphenyl, 4-butylphenyl (where "butylphenyl" means both n-butylphenyl, isobutylphenyl, sec-butylphenyl or tert-butylphenyl), 2,3-dimethylphenyl, 2,4-dimethylphenyl, 2,5-dimethylphenyl, 2,6-dimethylphenyl, 3,4-dimethylphenyl or 2-isopropyl-5-methylphenyl and Ar 2 for phenyl, 2-methylphenyl, 3-methylphenyl or 4-methylphenyl. In a particularly preferred embodiment, Ar 1 in formula (I) for 2-methylphenyl, 3-methylphenyl, 4-methylphenyl, 4-tert-butylphenyl or 2-isopropyl-5-methylphenyl and Ar 2 for phenyl, 2-methylphenyl, 3-methylphenyl, or 4-methylphenyl. In a further highly preferred embodiment, Ar 1in formula (I) for 2-methylphenyl, 3-methylphenyl, 4-methylphenyl, 2-isopropylphenol, 3-isopropylphenol, 4-isopropylphenol, 4-tert-butylphenyl or 2-isopropyl-5-methylphenyl and Ar 2 for phenyl. In an alternative, highly preferred embodiment, both Ar 1 as well as Ar 2 in formula (I) independently for 3-methylphenyl or 4-methylphenyl.

[0015] The thermoplastic molding compounds according to the invention may contain one or more phenylphosphonic acid diaryl esters of general formula (I).

[0016] Preferably, the phenylphosphonic acid diaryls 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 diaryls 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.

[0017] The phenylphosphonic acid diaryl 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 J. Macromol. Sci., Part B 2012, 51, 2141-2156, in which a solution of a phenol and triethylamine is treated with phenylphosphonic acid dichloride (PhP(O)Ch).

[0018] The thermoplastic molding compounds according to the invention contain thermoplastic (co-)polymer(s), preferably (co-)polymer(s) of 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, preferably polyvinyl chloride.

[0019] 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.

[0020] The molding compounds according to the invention contain 10 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).

[0021] The term (co-)polymer(s) stands for one or more copolymers and / or polymers, preferably for one or more polymers.

[0022] 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).

[0023] Typical plasticizers that can be used together with the phenylphosphonic acid diaryl 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 diacids. Other typical plasticizers are alkylsulfonic acid esters of phenol.

[0024] The thermoplastic molding compounds according to the invention represent flame-retardant, plasticized plastic compounds. A further object of the present invention is therefore the use of the phenylphosphonic acid diaryl esters according to formula (I) as a flame retardant, plasticizer and / or plasticizing flame retardant in plastics.

[0025] The molding compound according to the invention is used in coatings, films, floor coverings, cables, pipes, hoses, seals, conveyor belts, roofing membranes, adhesive tape films, tarpaulins, awnings and tents.

[0026] The (co)polymer(s) of the thermoplastic molding compounds according to the invention are particularly preferably polyvinyl chloride (PVC), i.e., compositions containing PVC which are in the form of granules, a powder, a paste, or a plastisol. These PVC molding compounds according to the invention are particularly preferably soft PVC. The PVC molding compounds according to the invention can be produced by mixing and compounding PVC with at least one phenylphosphonic acid diaryl 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.

[0027] The PVC molding compound according to the invention contains 10 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 PVC.

[0028] The PVC molding compound according to the invention is used in coatings, films, floor coverings, cables, pipes, hoses, seals, conveyor belts, roofing membranes, adhesive tape films, tarpaulins, awnings and tents.

[0029] 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.

[0030] The invention further 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

[0031] Determination of the acid number of phenylphosphonic acid esters

[0032] 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.

[0033] Examples of thesis

[0034] General synthesis procedure for the preparation of phenylphosphonic acid diaryl esters

[0035] Following the established procedure J. Macromol. Sei., Part B 2012, 51, 2141-2156, a solution of the phenolic building blocks 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 is complete, 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.

[0036] Synthesis example 1: Phenylphosphonic acid diphenyl ester

[0037] Prepared according to the general synthesis procedure from phenol (0.99 parts by weight), triethylamine (1.09 parts by weight), toluene (7.0 parts by weight), and phenylphosphonic acid dichloride (1.00 parts by weight). The acid value was 0.4 mg KOH / g.

[0038] Synthesis example 2: Phenylphosphonic acid bis-(4-tert-butylphenyl) ester

[0039] Prepared according to the general synthesis procedure from 4-tert-butylphenol (1.58 parts by weight), triethylamine (1.09 parts by weight), toluene (7.0 parts by weight), and phenylphosphonic acid dichloride (1.00 parts by weight). The acid value was 0.3 mg KOH / g. Synthesis example 3: Phenylphosphonic acid (4-tert-butylphenyl)(phenyl) ester

[0040] Prepared according to the general synthesis procedure from 4-tert-butylphenol (0.40 parts by weight), phenol (0.74 parts by weight), triethylamine (1.09 parts by weight), toluene (7.0 parts by weight), and phenylphosphonic acid dichloride (1.00 parts by weight). The acid value was <0.1 mg KOH / g.

[0041] Synthesis Example 4: Phenylphosphonic acid (3-methylphenyl)(4-methylphenyl) ester

[0042] Prepared according to the general synthesis procedure from 3-methylphenol (0.80 parts by weight), 4-methylphenol (0.34 parts by weight), triethylamine (1.08 parts by weight), toluene (7.0 parts by weight), and phenylphosphonic acid dichloride (1.00 parts by weight). The acid value was 0.39 mg KOH / g.

[0043] Synthesis Example 5: Phenylphosphonic acid (3 / 4-methylphenyl)(phenyl) ester

[0044] Prepared according to the general synthesis procedure from 3-methylphenyl (0.40 parts by weight), 4-methylphenyl (0.17 parts by weight), phenol (0.50 parts by weight), triethylamine (1.08 parts by weight), toluene (7.0 parts by weight), and phenylphosphonic acid dichloride (1.00 parts by weight). The acid value was 0.27 mg KOH / g.

[0045] Synthesis Example 6: Phenylphosphonic acid (2-isopropyl-5-methylphenyl)(phenyl) ester

[0046] Prepared according to the general synthesis procedure from 2-isopropyl-5-methylphenol (0.47 parts by weight), phenol (0.69 parts by weight), triethylamine (1.09 parts by weight), toluene (7.0 parts by weight), and phenylphosphonic acid dichloride (1.00 parts by weight). The acid value was <0.1 mg KOH / g.

[0047] Production of flexible PVC

[0048] 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 1), it was left on the roller until a layer formed. From the point of layer formation, the compounds were compounded for another 10 minutes on the rolling mill and finally removed as rolled sheets. The rolling temperature was 165°C. The test specimens for determining the LOI (Limit of Ingress) were produced from the rolled sheets 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.

[0049] The test specimens used to determine the compatibility and 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.

[0050] Table 1: Ingredients for the production of flexible PVC.

[0051] Component Function Description Quantity (parts by weight) A PVC Vinnol S4170 100

[0052] B Co-stabilizer EPO 65-1 2.5

[0053] epoxidized soybean oil

[0054] C PVC stabilizer Bärostab UBZ 780 RF 2.5

[0055] D Flame retardants Synthesis examples 1-6 55

[0056]

[0057] PVC samples were produced according to this regulation.

[0058] Determination of compatibility

[0059] In addition to the intended effectiveness of a polymer additive, such as flame retardancy, it is also expected that the additive will not have any negative effects on the other properties of the polymer. For example, the mechanical and optical properties of a polymer should be largely preserved. It is known to those skilled in the art that not every additive is compatible with every polymer. In the case of incompatibility, separation of the additive and polymer can occur after processing, manifesting as solid or liquid deposits of the additive on the surface of the polymer compound. Those skilled in the art refer to this as blooming (solid deposits) or exudation (liquid deposits). Such incompatibilities are usually clearly visible and result in an undesirable material appearance: Liquid deposits produce a greasy, shiny surface and a moist, greasy feel. Solid deposits create a mostly white, solid coating.In both cases, the homogeneity of the compound suffers. Cloudy areas with impaired transparency are typical when there is an incompatibility with flexible PVC.

[0060] To determine compatibility, the PVC compounds were stored for 4 weeks at 23°C and 50% humidity and then visually assessed.

[0061] Determination of flame retardancy

[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. It represents the minimum oxygen concentration in a nitrogen / oxygen mixture below which combustion of a test specimen can just barely 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. For practical application, a value of at least 30 should be achieved in the test.

[0063] Determination of the plasticizer effect

[0064] 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. A Shore A hardness of less than 95 is considered an indicator of a plasticizing effect.

[0065] The results of the measurements are summarized in Table 2.

[0066] Table 2: Determination of compatibility, flame retardancy and Shore A hardness of the manufactured PVC samples

[0067] Flame retardant compatibility Shore A - Example LOI (Component D) ity Hardness V1

[0068] S1 - nbnb (comparative example)

[0069] V2

[0070] S2 - nbnb (comparative example)

[0071]

[0072] V3

[0073] S3 + 32.6 90 (according to the invention)

[0074] V4

[0075] S4 + 32.3 82 (according to the invention)

[0076] V5

[0077] S5 + 33.8 84 (according to the invention)

[0078] V6

[0079] S6 + 33.2 92 (according to the invention)

[0080]

[0081] nb = not determined.

[0082] The results show that the phenylphosphonic acid diphenyl ester S1 known from EP 0043482 A2 and the phenylphosphonic acid bis(4-tert-butylphenyl) ester S2 known from US 2009 149587 A1 are unsuitable for the production of flame-retardant flexible PVC. Due to poor compatibility, the corresponding PVC compounds V1 and V2 are not sufficiently stable. The flame retardancy and plasticizing effect of these PVC compounds were therefore not determined in detail. In contrast, the PVC compounds V3-V6 according to the invention are stable; that is, the phenylphosphonic acid diaryl esters S3-S6 used in their production are sufficiently compatible with PVC. They exhibit sufficient flame retardancy (LOI value >30) while simultaneously showing good plasticizing effect (Shore A hardness <95).

Claims

Patent claims 1. Thermoplastic molding compounds containing thermoplastic (co-)polymer(s) and, based on 100 parts by weight of thermoplastic (co-)polymer(s), 10 to 150 parts by weight of at least one phenylphosphonic acid diaryl ester of general formula (I) OO— Ar 1 in which Ar 1 for a singly or multiply alkyl-substituted aryl group with a total of 7 - 10 carbon atoms and Ar 2 stands for phenyl or 2-M ethyl phenyl, 3-methylphenyl or 4-methylphenyl.

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 Ar 1in formula (I) for 2-methylphenyl, 3-methylphenyl, 4-methylphenyl, 2-ethylphenyl, 3-ethylphenyl, 4-ethylphenyl, 2-propylphenyl, 3-propylphenyl, 4-propylphenyl, 2-butylphenyl, 3-butylphenyl, 4-butylphenyl, 2,3-dimethylphenyl, 2,4-dimethylphenyl, 2,5-dimethylphenyl, 2,6-dimethylphenyl, 3,4-dimethylphenyl or 2-isopropyl-5-methylphenyl and Ar 2 stands for phenyl, 2-methylphenyl, 3-methylphenyl or 4-methylphenyl.

5. Thermoplastic molding compounds according to one or more of claims 1-3, characterized in that Ar 1 in formula (I) for 2-methylphenyl, 3-methylphenyl, 4-methylphenyl, 4-tert-butylphenyl or 3-isopropyl-5-methylphenyl and Ar 2 stands for phenyl or 2-methylphenyl, 3-methylphenyl, 4-methylphenyl.

6. Thermoplastic molding compounds according to one or more of claims 1-3, characterized in that Ar 1in formula (I) for 2-methylphenyl, 3-methylphenyl, 4-methylphenyl, 4-tert-butylphenyl or 3-isopropyl-5-methylphenyl and Ar 2 stands for phenyl.

7. Thermoplastic molding compounds according to one or more of claims 1-3, characterized in that Ar 1 and Ar 2 in formula (I) stand independently for 2-methylphenyl, 3-methylphenyl or 4-methylphenyl.

8. Thermoplastic molding compounds according to one or more of claims 2-7 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.

9. Molding compounds according to one or more of claims 1-8, 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 diaryl esters of formula (I) based on 100 parts by weight of thermoplastic (co-)polymer(s).

10. Use of molding compounds according to one or more of claims 1 to 9 for the manufacture of coatings, films, floor coverings, cables, pipes, hoses, seals, conveyor belts, roofing membranes, adhesive tape films, tarpaulins, awnings or tents.

11. 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 9 are used.

12. 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 9 or obtainable by the method according to claim 11.

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