Flame-retardant polyamide composite material, and preparation method and application thereof

Abstract

The present application relates to a kind of flame-retardant polyamide composite and its preparation method and application, belong to the composition technical field of polymer compound.The flame-retardant polyamide composite of the present application includes the following components by weight fraction: polyamide resin 54~82 parts, melamine cyanurate 8~15 parts, chain extender 2~4 parts, colorant 0.1~1 part;The end amino group content of the polyamide resin is 20~100mmol / kg;The contact angle of the colorant is ≤40 ° and pH value is 5.5~7.5.The flame-retardant polyamide composite has high flame-retardant, high moisture and heat aging resistance and good color stability.

Description

Technical Field

[0001] This invention relates to the field of polymer composition technology, specifically to a flame-retardant polyamide composite material, its preparation method, and its application. Background Technology

[0002] Polyamides possess excellent mechanical properties, abrasion resistance, and chemical corrosion resistance, making them widely used in automotive, communications, electronics, mechanical parts, and packaging films. However, unmodified polyamides ignite rapidly upon contact with an open flame, releasing significant amounts of heat and dense smoke, accompanied by dripping during combustion, posing serious safety hazards. Environmentally friendly nitrogen-based flame retardants such as melamine cyanurate (MCA) have become the mainstream choice due to their high efficiency, low smoke, and halogen-free nature. However, their unique condensed-phase flame retardant mechanism (relying on acidity to promote localized matrix degradation and dripping) inevitably catalyzes the thermal degradation of polyamides themselves while imparting flame retardancy. This is especially true for recycled polyamides, which have undergone multiple processing steps resulting in lower molecular weights and are prone to interacting with acidic MCA, accelerating thermal degradation or neutralizing acidic sites to weaken flame retardant efficiency. Furthermore, recycled polyamides can affect the color stability of colorants in humid and hot environments, making it difficult for polyamide composites to simultaneously possess high flame retardancy, resistance to humid and hot aging, and good color stability. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide a flame-retardant polyamide composite material, its preparation method, and its application.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows: In a first aspect, the present invention provides a flame-retardant polyamide composite material, comprising the following components by weight: 54-82 parts of polyamide resin, 8-15 parts of melamine cyanurate, 2-4 parts of chain extender, and 0.1-1 parts of colorant; The polyamide resin has a terminal amino content of 20~100 mmol / kg; The colorant has a contact angle ≤40° and a pH value of 5.5~7.5.

[0005] The inventors discovered that by controlling the contact angle and pH value of the colorant within a suitable range and combining it with a chain extender, they can effectively inhibit the co-precipitation of the colorant along with the decomposition products of melamine cyanurate during the processing and molding process. Furthermore, the acidity or alkalinity of the colorant can be used to balance the pH of the system, thus mitigating the degradation of polyamide resin while fully ensuring the acidic catalytic flame-retardant performance of melamine cyanurate. On the other hand, the chain extender stabilizes the end groups of the polyamide resin and rapidly captures free radicals during the degradation process, effectively controlling the chain-breaking degradation and cross-linking reaction of the polyamide resin. This results in flame-retardant polyamide composite materials that possess high flame retardancy, high resistance to damp heat aging, and good color stability.

[0006] The terminal amino content of polyamide resin can be determined by acid-base titration, which includes the following steps: The test was conducted using a fully automated point titrator. 0.5 g of polyamide resin was taken, and 45 mL of phenol and 3 mL of anhydrous methanol were added. The solution was heated to reflux at 90 °C to dissolve the resin, and the insoluble matter was filtered off while it was still hot. After the filtrate was cooled to room temperature (25 °C), the content of the terminal amino groups was titrated with a hydrochloric acid standard solution of a calibrated concentration.

[0007] Terminal amino group content (mmol / kg) = (C×V×1000) / m; Where C is the hydrochloric acid concentration (mol / L), V is the volume of hydrochloric acid consumed (mL), and m is the sample mass (g).

[0008] In some embodiments, the contact angle of the colorant may be, but is not limited to, any or both of the following values: 0°, 1°, 2°, 3°, 4°, 5°, 6°, 7°, 8°, 9°, 10°, 11°, 12°, 13°, 14°, 15°, 16°, 17°, 18°, 19°, 20°, 21°, 22°, 23°, 24°, 25°, 26°, 27°, 28°, 29°, 30°, 31°, 32°, 33°, 34°, 35°, 36°, 37°, 38°, 39°, and 40°.

[0009] The contact angle of a colorant can be measured using the following methods: According to ASTM D7334-2022, the colorant powder is pressed into a smooth and compact sheet at 10 MPa using the pressing method. Then, the contact angle is measured using a contact angle meter, and the contact angle is calculated by measuring the wetting of water on the surface of the sheet.

[0010] In some embodiments, the pH value of the colorant may be, but is not limited to, any one or any two of the following: 5.5, 5.6, 5.7, 5.8, 5.9, 6, 6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 6.8, 6.9, 7, 7.1, 7.2, 7.3, 7.4, 7.5.

[0011] The pH value of a colorant can be measured using the following methods: The method adopted was based on the international standard ISO 787-9:2019, "Pigments and extender pigments – General test methods – Part 9: Determination of pH of aqueous suspensions". A 10% (w / w) pigment suspension was prepared in a glass container with anhydrous ethanol. The container was stopped, vigorously shaken for 1 minute, and then allowed to stand for 5 minutes. The stopper was removed, and the pH of the suspension was measured at 30°C, accurate to 0.1 units.

[0012] It should also be noted that polyamide resin is the main resin in flame-retardant polyamide composites, and its mass content in flame-retardant polyamide composites is ≥55%.

[0013] In some embodiments, the weight parts of polyamide resin in the flame-retardant polyamide composite material may be, but are not limited to, any one or any two of the following values: 54 parts, 55 parts, 56 parts, 57 parts, 58 parts, 59 parts, 60 parts, 61 parts, 62 parts, 63 parts, 64 parts, 65 parts, 66 parts, 67 parts, 68 parts, 69 parts, 70 parts, 71 parts, 72 parts, 73 parts, 74 parts, 75 parts, 76 parts, 77 parts, 78 parts, 79 parts, 80 parts, 81 parts, and 82 parts.

[0014] In some embodiments, the weight parts of melamine cyanurate in the flame-retardant polyamide composite material may be, but are not limited to, any one or any two of the following values: 8 parts, 8.5 parts, 9 parts, 9.5 parts, 10 parts, 10.5 parts, 11 parts, 11.5 parts, 12 parts, 12.5 parts, 13 parts, 13.5 parts, 14 parts, 14.5 parts, and 15 parts.

[0015] In some embodiments, the weight percentage of the chain extender in the flame-retardant polyamide composite material may be, but is not limited to, any one or any two of the following values: 2 parts, 2.1 parts, 2.2 parts, 2.3 parts, 2.4 parts, 2.5 parts, 2.6 parts, 2.7 parts, 2.8 parts, 2.9 parts, 3 parts, 3.1 parts, 3.2 parts, 3.3 parts, 3.4 parts, 3.5 parts, 3.6 parts, 3.7 parts, 3.8 parts, 3.9 parts, and 4 parts.

[0016] In some embodiments, the weight parts of the colorant in the flame-retardant polyamide composite material may be, but are not limited to, any one or any two of the following values: 0.1 parts, 0.2 parts, 0.3 parts, 0.4 parts, 0.5 parts, 0.6 parts, 0.7 parts, 0.8 parts, 0.9 parts, and 1 part.

[0017] In some embodiments, the terminal amine content of the polyamide resin may be, but is not limited to, 20 mmol / kg, 22 mmol / kg, 24 mmol / kg, 26 mmol / kg, 28 mmol / kg, 30 mmol / kg, 32 mmol / kg, 34 mmol / kg, 36 mmol / kg, 38 mmol / kg, 40 mmol / kg, 42 mmol / kg, 44 mmol / kg, 46 mmol / kg, 48 mmol / kg, 50 mmol / kg, 52 mmol / kg, 54 mmol / kg, 56 mmol / kg, or 58 mmol / kg. The range of any one or any two of the following values: 60 mmol / kg, 62 mmol / kg, 64 mmol / kg, 66 mmol / kg, 68 mmol / kg, 70 mmol / kg, 72 mmol / kg, 74 mmol / kg, 76 mmol / kg, 78 mmol / kg, 80 mmol / kg, 82 mmol / kg, 84 mmol / kg, 86 mmol / kg, 88 mmol / kg, 90 mmol / kg, 92 mmol / kg, 94 mmol / kg, 96 mmol / kg, 98 mmol / kg, and 100 mmol / kg.

[0018] As a preferred embodiment of the flame-retardant polyamide composite material of the present invention, it comprises the following components by weight: 60-75 parts of polyamide resin, 10-13 parts of melamine cyanurate, 2.5-3.5 parts of chain extender, and 0.3-0.8 parts of colorant.

[0019] In a preferred embodiment of the flame-retardant polyamide composite material of the present invention, the relative viscosity of the polyamide resin is 1.5 to 4.

[0020] When the relative viscosity of the polyamide resin is within the above range, it can not only ensure the fluidity of the flame-retardant polyamide composite material during melt processing, thereby promoting the uniform dispersion of melamine cyanurate and colorant to improve the flame-retardant performance and color stability of the flame-retardant polyamide composite material, but also help to alleviate the thermal oxidative degradation of the polyamide resin and improve the resistance to humid heat aging of the flame-retardant polyamide composite material.

[0021] In some embodiments, the relative viscosity of the polyamide resin may be, but is not limited to, a range of any one or both of the following: 1.5, 1.6, 1.7, 1.8, 1.9, 2, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.

[0022] The relative viscosity of polyamide resin can be measured by the following methods: Weigh 0.5g of polyamide resin and transfer it to a 50mL volumetric flask. Add approximately 40mL of 96% concentrated sulfuric acid and sonicate until the polyamide resin is completely dissolved. Cool the solution to 25°C, dilute it to the mark with concentrated sulfuric acid, and mix thoroughly. Measure the flow time of the 0.01g / mL polyamide resin solution at 25°C through an Ubbelohde viscometer and record it as t1. Measure the flow time of the concentrated sulfuric acid solvent using the same viscometer and record it as t2. t1 / t2 is the relative viscosity.

[0023] In a preferred embodiment of the flame-retardant polyamide composite material of the present invention, the end-amino content of the polyamide resin is 23~85 mmol / kg.

[0024] In a preferred embodiment of the flame-retardant polyamide composite material of the present invention, the polyamide resin includes at least one of virgin polyamide resin and recycled polyamide resin.

[0025] As a preferred embodiment of the flame-retardant polyamide composite material of the present invention, the polyamide resin includes at least one of PA66, PA612, PA610, PA1010, PA1012, PA1212, PPTA, PA6T, PA10T, PA6I / 6T, PA10T / 1012, PAMXD10, and PAMXD6. And / or, the chain extender is selected from at least one of bis / polyepoxy functional group chain extenders, bis / polyoxazoline chain extenders, bis / polyanhydride chain extenders, and diisocyanate chain extenders; And / or, the colorant includes at least one of iron oxide red, quinacridone, and metallic chromium complex azo dyes, or a mixture thereof with at least one of ultramarine, perylene, and phthalocyanine blue dyes.

[0026] As a preferred embodiment of the flame-retardant polyamide composite material of the present invention, it further comprises the following components by weight: 10-20 parts of reinforcing fiber, 1-2 parts of antioxidant, and 0.1-0.5 parts of lubricant.

[0027] In some embodiments, the weight percentage of reinforcing fibers in the flame-retardant polyamide composite material may be, but is not limited to, any one or both of the following ranges: 10 parts, 11 parts, 12 parts, 13 parts, 14 parts, 15 parts, 16 parts, 17 parts, 18 parts, 19 parts, and 20 parts.

[0028] In some embodiments, the reinforcing fiber includes, but is not limited to, at least one of glass fiber and carbon fiber.

[0029] In some embodiments, the average length of the reinforcing fiber is 3 to 6 mm.

[0030] In some embodiments, the weight parts of antioxidant in the flame-retardant polyamide composite material may be, but are not limited to, any one or both of the following ranges: 1 part, 1.1 parts, 1.2 parts, 1.3 parts, 1.4 parts, 1.5 parts, 1.6 parts, 1.7 parts, 1.8 parts, 1.9 parts, and 2 parts.

[0031] In some embodiments, the antioxidant includes, but is not limited to, at least one of antioxidant 1098, antioxidant 1010, and antioxidant 168.

[0032] In some embodiments, the weight percentage of the lubricant in the flame-retardant polyamide composite material may be, but is not limited to, any one or both of 0.1 parts, 0.2 parts, 0.3 parts, 0.4 parts, and 0.5 parts.

[0033] In some embodiments, the lubricant includes, but is not limited to, at least one of stearate, stearyl erucamide, polysiloxane, and fluorinated compounds.

[0034] Secondly, the present invention provides a method for preparing the above-mentioned flame-retardant polyamide composite material, comprising the following steps: mixing the components uniformly and melting and extruding to obtain the flame-retardant polyamide composite material.

[0035] In some embodiments, a twin-screw extruder can be used for melt extrusion, wherein the length-to-diameter ratio of the screw of the twin-screw extruder is 40:1 to 48:1, the barrel temperature is 270 to 300°C, and the screw speed is 150 to 400 rpm.

[0036] Thirdly, the present invention provides an application of the above-mentioned flame-retardant polyamide composite material in the preparation of automotive parts, outdoor sports equipment, new energy charging facilities, electronic and electrical housings and components, colored tableware and kitchenware.

[0037] Fourthly, the present invention provides a colored nylon part comprising the above-mentioned flame-retardant polyamide composite material.

[0038] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention, by controlling the contact angle and pH value of the colorant within a suitable range and combining them with a chain extender, can effectively inhibit the co-precipitation of the colorant with the decomposition products of melamine cyanurate during processing and molding. It also utilizes the acidity and alkalinity of the colorant to balance the pH of the system, thus mitigating polyamide resin degradation while fully ensuring the acidic catalytic flame-retardant performance of melamine cyanurate. Furthermore, the chain extender stabilizes the end groups of the polyamide resin and rapidly captures free radicals during polyamide resin degradation, thereby effectively controlling the chain-breaking degradation and cross-linking reaction of the polyamide resin. This results in flame-retardant polyamide composite materials that possess high flame retardancy, high resistance to damp heat aging, and good color stability. Detailed Implementation

[0039] To better illustrate the purpose, technical solution, and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0040] Unless otherwise specified, all other materials, reagents, etc. used in the examples and comparative examples are commercially available.

[0041] 1. Raw materials and reagents 1) Polyamide resin Polyamide resin 1 (PA6): terminal amino content is 23.6 mmol / kg, relative viscosity is 2.0, grade PA6 M2000, manufacturer is Xinhui Meida; Polyamide resin 2 (PA6): obtained by aging polyamide resin 1 at 100℃ for 1000h, the content of terminal amino groups was measured to be 37.7mmol / kg, and the relative viscosity was 1.9; Polyamide resin 3 (PA66): terminal amino content is 40.2 mmol / kg, relative viscosity is 2.4, grade PA66EPR24, manufacturer is China Pingmei Shenma Holding Group Co., Ltd.; Polyamide resin 4 (PA66): terminal amino content is 82.0 mmol / kg, relative viscosity is 2.7, grade PA66EP158NH, manufacturer Huafeng Group; Polyamide resin 5 (PA6): terminal amino content is 17 mmol / kg, relative viscosity is 4.0, grade PA6 BL40H, manufacturer Yueyang Petrochemical; Polyamide resin 6 (PA6): terminal amino content is 120 mmol / kg, relative viscosity is 2.0, grade PA6 J2000NH, manufacturer is Juheshun.

[0042] 2) Flame retardants The flame retardant is melamine cyanurate, MCA-F, purchased from Sichuan Fine Chemical Research and Design Institute.

[0043] 3) Chain extenders Chain extender 1 is 1,4-butanediol diglycidyl ether, CAS: 2425-79-8, Aladdin; Chain extender 2 is toluene diisocyanate, CAS: 26471-62-5, Macklin reagent.

[0044] 4) Coloring agents Colorant 1 is iron oxide red, with a contact angle of 0° and a pH of 6.8; Colorant 2 is a chromium complex azo dye with a contact angle of 37° and a pH of 5.8; Colorant 3 is composed of a chromium complex azo dye and ultramarine dye in a mass ratio of 2:1, with a contact angle of 29° and a pH of 5.7. Colorant 4 is composed of iron oxide red and perylene series in a mass ratio of 1:1, with a contact angle of 39° and a pH of 6.5; Colorant 5 is a violet-based colorant with a contact angle of 7° and a pH of 4.7. Colorant 6 is a perylene series, with a contact angle of 61° and a pH of 6.2; Colorant 7 is a phthalocyanine blue derivative with a contact angle of 81° and a pH of 9.3; The sources of the aforementioned iron oxide red, metallic chromium complex azo dyes, ultramarine violet, perylene series, and phthalocyanine blue dyes are as follows: Iron oxide red: Grade R206, manufacturer: Guangzhou Xinghui Trading Co., Ltd.; Chromium complex azo dyes: Grade R297, manufactured by Guangzhou Aoying Trading Co., Ltd. Ultramarine: Grade V601, Manufacturer: Guangzhou Xinxinghui Chemical Co., Ltd.; Perylene series: Grade K3911, manufacturer BASF; Phthalocyanine Blue: Grade BF1535, manufacturer: Shenzhen Dingtai Chemical Co., Ltd.

[0045] 5) Reinforcing fibers The reinforcing fiber is glass fiber with an average length of 3mm, grade S1HM435TM-10-3, and manufactured by Taishan Glass Fiber Co., Ltd.

[0046] 6) Antioxidants The antioxidant was RIANOX 1098, purchased from Tianjin Lialong New Materials Co., Ltd.

[0047] 7) Lubricant The lubricant is stearyl stearate, brand name LOXIOL G32, manufactured by Corning, Germany.

[0048] 2. Preparation method of the flame-retardant polyamide composite material of the present invention According to the formula, the components are mixed and then added to a twin-screw extruder for melt extrusion to obtain a flame-retardant polyamide composite material; wherein, the temperature range of the twin-screw extruder is 270℃ to 300℃, and the screw speed is 400 rpm.

[0049] 3. Performance Testing 1) Flame retardant performance: The flame retardant polyamide composite materials of each embodiment and comparative example were injection molded into vertical burning test strips of 125mm×13mm×0.8mm, and their flame retardant performance was tested according to UL 94-2021 standard.

[0050] 2) Resistance to damp heat aging: According to ISO 527-2-2012 standard, the flame-retardant polyamide composite materials of each embodiment and comparative example were injection molded into 1BA tensile test strips with a thickness of 3.0 mm. Ten 1BA tensile test strips were prepared for each embodiment or comparative example and randomly divided into two groups, A and B (i.e., 5 in group A and 5 in group B). The initial tensile strength of group A was directly tested (tensile rate of 50 mm / min) to obtain the arithmetic mean. The tensile strength of group B was first aged in an aging chamber at a temperature of 85℃ and a humidity of 85% for 144 h and then tested (tensile rate of 50 mm / min) to obtain the tensile strength after aging (arithmetic mean). Tensile strength retention rate = (Tensile strength after aging / Initial tensile strength) × 100% The tensile strength retention rate is used to evaluate the damp heat aging resistance of flame-retardant polyamide composites. The higher the tensile strength retention rate, the better the damp heat aging resistance of the flame-retardant polyamide composites.

[0051] 3) Water Boiling Color Difference: The flame-retardant polyamide composite materials of each embodiment and comparative example were injection molded into color plates with dimensions of 60mm×60mm×2mm. The L, a, and b values ​​were tested according to CIE 2000, where L represents lightness / darkness, a represents red / green, and b represents yellow / blue. These values ​​were recorded as L1, a1, and b1. The color plates were then placed in a 90℃ water boiling chamber for 6 hours, and the L, a, and b values ​​were tested again and recorded as L2, a2, and b2. The water boiling color difference ΔE was obtained, where ΔE = [(L2-L1)]. 2 +(a2-a1) 2 +(b2-b1) 2 ] 0.5 .

[0052] Table 1 shows the weight proportions and properties of each component in the flame-retardant polyamide composites in Examples 1 to 8. Table 2 shows the weight proportions and properties of each component in the flame-retardant polyamide composites in Examples 9 to 13. Table 3 shows the weight parts and properties of each component in the flame-retardant polyamide composites of Comparative Examples 1 to 6. The " / " in Tables 1, 2 and 3 indicates that there are no relevant parameters.

[0053] According to the data in Tables 1-3, the flame retardant polyamide composite materials in Examples 1-13 all achieved a flame retardant rating of V-0 and a tensile strength retention rate of ≥94%, while the color difference ΔE after boiling was ≤2.4, indicating that the flame retardant polyamide composite material of the present invention has high flame retardancy, high resistance to humid heat aging and good color stability.

[0054] Comparative Examples 1 and 2 show that while excessively low or high terminal amino content in polyamide resins has little impact on the flame-retardant properties of flame-retardant polyamide composites, it significantly reduces their resistance to humid heat aging and color stability. Comparative Examples 3, 4, and 5 show that when the contact angle of the colorant is greater than 40° or its pH value is outside the range of 5.5 to 7.5, it not only fails to effectively improve the resistance to humid heat aging of flame-retardant polyamide composites but also significantly deteriorates their color stability. Comparative Example 6 also shows that the lack of chain extender components also significantly reduces the resistance to humid heat aging and color stability of flame-retardant polyamide composites.

[0055] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A flame-retardant polyamide composite material, characterized in that, By weight, it includes the following components: 54-82 parts of polyamide resin, 8-15 parts of melamine cyanurate, 2-4 parts of chain extender, and 0.1-1 parts of colorant; The polyamide resin has a terminal amino content of 20~100 mmol / kg; The colorant has a contact angle ≤40° and a pH value of 5.5~7.

5.

2. The flame-retardant polyamide composite material as described in claim 1, characterized in that, By weight, it includes the following components: 60-75 parts polyamide resin, 10-13 parts melamine cyanurate, 2.5-3.5 parts chain extender, and 0.3-0.8 parts colorant.

3. The flame-retardant polyamide composite material as described in claim 1, characterized in that, The relative viscosity of the polyamide resin is 1.5~4.

4. The flame-retardant polyamide composite material as described in claim 1, characterized in that, The polyamide resin has a terminal amino content of 23~85 mmol / kg.

5. The flame-retardant polyamide composite material as described in claim 1, characterized in that, The polyamide resin includes at least one of virgin polyamide resin and recycled polyamide resin.

6. The flame-retardant polyamide composite material as described in claim 1, characterized in that, The polyamide resin includes at least one of PA66, PA612, PA610, PA1010, PA1012, PA1212, PPTA, PA6T, PA10T, PA6I / 6T, PA10T / 1012, PA MXD10, and PA MXD6; And / or, the chain extender is selected from at least one of bis / polyepoxy functional group chain extenders, bis / polyoxazoline chain extenders, bis / polyacid anhydride chain extenders, and diisocyanate chain extenders; And / or, the colorant includes at least one of iron oxide red, quinacridone, and metallic chromium complex azo dyes, or a mixture thereof with at least one of ultramarine, perylene, and phthalocyanine blue dyes.

7. The flame-retardant polyamide composite material as described in claim 1, characterized in that, By weight, it also includes the following components: 10-20 parts reinforcing fiber, 1-2 parts antioxidant, and 0.1-0.5 parts lubricant.

8. A method for preparing the flame-retardant polyamide composite material according to any one of claims 1 to 7, characterized in that, Includes the following steps: The components are mixed evenly and melted and extruded to obtain a flame-retardant polyamide composite material.

9. The application of the flame-retardant polyamide composite material according to any one of claims 1 to 7 in the preparation of automotive parts, outdoor sports equipment, new energy charging facilities, electronic and electrical housings and components, colored tableware and kitchenware.

10. A colored nylon part, characterized in that, Including the flame-retardant polyamide composite material according to any one of claims 1 to 7.

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