Use of organosilicon polymers containing siloxa octamers in flame retardant materials

Abstract

The application relates to the technical field of flame-retardant materials, in particular to application of an organic silicon polymer containing a siloxane eight-membered ring in a flame-retardant material and a fireproof glass. The application further increases the reticulation structure of the organic silicon polymer through self-polymerization or cross-linking reaction of the organic silicon polymer, further improves the flame-retardant property of the organic silicon polymer, the annular structure of the organic silicon polymer containing the siloxane eight-membered ring contains a large number of siloxane bonds, has excellent flame-retardant property, and can greatly improve the flame-retardant property and fire resistance of the flame-retardant material when applied to the flame-retardant material.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of flame-retardant materials, in particular to application of organic silicon polymer containing siloxane octacycle in flame-retardant materials and a fireproof glass. BACKGROUND

[0002] Flame-retardant materials have become one of the important driving forces for the development of polymer materials, and the use amount is only next to plasticizers. At present, the flame-retardant materials commonly used in polymers are mainly halogen and phosphorus flame-retardant materials. The application of halogen flame-retardant materials is limited in some fields due to the harmful gases generated during combustion. Developing new high-efficiency, low-toxicity halogen-free flame-retardant materials has become a hot spot in the research of flame-retardant materials. Since phosphorus flame-retardant materials have many advantages, people initially put their hopes on organic phosphorus flame-retardant materials to realize halogen-free flame-retardant materials, which promotes the development of phosphorus flame-retardant materials. However, it has been proved that organic phosphorus flame-retardant materials also have certain shortcomings, such as great polarity, easy moisture absorption, poor high-temperature resistance, and large smoke generation.

[0003] Fireproof glass is a special glass that can maintain its integrity in a specified fire resistance test. Its main role in fire prevention is to control the spread of fire or smoke, and it is a measure-type fireproof material. Its fireproof effect is evaluated by fire resistance performance. It is a special glass that can maintain its integrity and heat insulation performance in a specified fire resistance test through special processing and treatment. The original sheet glass of fireproof glass can be made of float plane glass, tempered glass, and composite fireproof glass, which can also be made of single-piece fireproof glass.

[0004] At present, acrylamide monomer is mainly used as the raw material of fireproof glass. It not only has toxicity to the human body and causes environmental pollution, but also has poor weather resistance and fire resistance and heat insulation performance, short service life, and low burn test pass rate. These factors greatly limit the use of organic composite fireproof glass. SUMMARY

[0005] The present application is based on the inventors' discovery and understanding of the following facts and problems: the existing fireproof glass has various types, but the manufacturing cost and use performance of many glasses are not competitive, which makes the production efficiency of the product not good, and the existing flame-retardant glass will burst after a long time of burning. The fireproof way of the existing fireproof glass includes increasing the thickness of the glass or setting a flame-retardant coating interlayer in the glass. Increasing the thickness of the glass will greatly increase the difficulty and cost of production and installation, and the glass with a flame-retardant coating interlayer has to increase the thickness of the coating due to the limited flame-retardant effect of the flame-retardant coating, which still cannot effectively reduce the production cost of the glass. Therefore, it is necessary to develop a product with high cost performance, low cost and good fire resistance.

[0006] The present application aims to at least solve one of the problems in the related art. To this end, the embodiments of the present application propose an application of a siloxane octacycle-containing organosilicon polymer in a flame-retardant material and a fireproof glass, by further self-polymerization or cross-linking of the organosilicon polymer, the network structure of the polymer is increased, and the flame-retardant property of the organosilicon polymer is effectively improved.

[0007] The application of the siloxane octacycle-containing organosilicon polymer in the flame-retardant material according to the embodiments of the present application, the polymer comprises a general structure shown in formula I,

[0008]

[0009] wherein R1, R2, R4, R5, R6, R7 are each independently selected from at least one of optionally substituted alkyl, optionally substituted cycloalkyl, optionally substituted heterocyclyl, optionally substituted phenyl, optionally substituted heteroaryl;

[0010] R3, R8 are each independently selected from at least one of optionally substituted alkyl, optionally substituted alkenyl, optionally substituted cycloalkenyl, optionally substituted heterocyclyl, optionally substituted aryl, optionally substituted heteroaryl, optionally substituted cyclohexyl;

[0011] m is independently an arbitrary value between 2 and 3000000, and n is independently an arbitrary value between 0 and 3000000;

[0012] The application of the siloxane octacycle-containing organosilicon polymer in the flame-retardant material according to the embodiments of the present application has the following advantages and technical effects: 1. The ring structure of the siloxane octacycle-containing organosilicon polymer in the embodiments of the present application contains a large number of siloxane bonds, and the application in the flame-retardant material can greatly improve the flame retardancy and fire resistance of the flame-retardant material; 2. The octacycle of the embodiments of the present application makes the spatial arrangement of the polymer compact, and effectively improves the flame-retardant property of the polymer.

[0013] In some embodiments of the present application, m is independently an arbitrary value between 30000 and 3000000.

[0014] In some embodiments of the present application, at least one of R1-R8 is selected from optionally substituted aryl, and preferably, at least one of R3 and R8 is selected from optionally substituted aryl.

[0015] In some embodiments of the present application, at least one of R3 and R8 is selected from optionally substituted alkenyl.

[0016] In some embodiments of the present application, the polymer is subjected to self-polymerization under the action of a catalyst, or cross-linking reaction by adding a polymerization monomer.

[0017] In some embodiments of the present application, the polymerized monomer contains at least one of a silicon-hydrogen bond, a silicon-hydroxyl bond, or a siloxane bond.

[0018] In some embodiments of the present application, the polymerized monomer contains at least two silicon-hydrogen bonds, a silicon-hydroxyl bond, or a siloxane bond.

[0019] In some embodiments of the present application, the polymerized monomer is selected from at least one of a phenyl tri(dimethylsiloxane silyl silane), a diphenyl silicon hydride, or a phenyl silane.

[0020] In some embodiments of the present application, the catalyst is selected from at least one of B(C6F5)3, Karstedt's catalyst, platinum oxide, chloroplatinic acid, potassium hydroxide, a radical initiator, an organotin compound, anhydrous zinc chloride, or a nickel metal.

[0021] A fireproof glass according to an embodiment of the present application comprises a glass substrate and a fire-retardant coating, the fire-retardant coating comprising the fire-retardant material described above.

[0022] The fireproof glass according to an embodiment of the present application has the advantages and technical effects that: the use of the organosilicon polymer containing a siloxane eight-membered ring with high fire-retardant performance significantly improves the fire resistance, heat insulation, and thermal shock resistance of the fireproof glass, and the fireproof glass according to the embodiment of the present application can remain intact without breaking in a long-time burning environment. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is a structural schematic diagram of the fireproof glass according to an embodiment of the present application.

[0024] Reference signs: 1-glass substrate, 2-fire-retardant coating. DETAILED DESCRIPTION

[0025] Embodiments of the present application are described in detail below, examples of which are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to explain the present application, and cannot be understood as a limitation of the present application.

[0026] Application of the organosilicon polymer containing a siloxane eight-membered ring in a fire-retardant material according to an embodiment of the present application, the polymer comprises a general structure shown in Formula I,

[0027]

[0028] wherein R1, R2, R4, R5, R6, R7 are each independently selected from at least one of an optionally substituted alkyl group, an optionally substituted cycloalkyl group, an optionally substituted heterocyclic group, an optionally substituted phenyl group, and an optionally substituted heteroaryl group;

[0029] R3, R8 are each independently selected from at least one of optionally substituted alkyl, optionally substituted alkenyl, optionally substituted cycloalkenyl, optionally substituted heterocyclyl, optionally substituted aryl, optionally substituted heteroaryl, optionally substituted cyclohexyl;

[0030] m is independently selected from any value between 2 and 3000000, preferably 30000-3000000, n is independently selected from any value between 0 and 3000000, preferably n = 0;

[0031] The organic silicon polymer containing siloxane eight-membered ring in the embodiment of the application is the organic silicon polymer disclosed in CN107759791A, and is obtained by using the preparation method disclosed in CN107759791A.

[0032] The application of the organic silicon polymer containing siloxane eight-membered ring in the embodiment of the application in a flame-retardant material: the organic silicon polymer containing siloxane eight-membered ring disclosed in CN107759791A contains a large number of siloxane bonds on the ring structure, and application in a flame-retardant material can greatly improve the flame retardance and fire resistance of the flame-retardant material; the eight-membered ring in the embodiment of the application makes the spatial arrangement of the polymer compact, and effectively improves the flame-retardant performance of the polymer.

[0033] In some embodiments of the application, m is independently selected from any value between 30000 and 3000000. In the embodiment of the application, m is preferably 30000-3000000, which can significantly improve the flame-retardant performance and prolong the flame-retardant time.

[0034] In some embodiments of the application, at least one of R1-R8 is selected from optionally substituted aryl, and preferably at least one of R3 and R8 is selected from optionally substituted aryl. In the application of the embodiment of the application, the introduction of aryl can greatly improve the flame retardance of the organic silicon polymer.

[0035] In some embodiments of the application, at least one of R3 and R8 is selected from optionally substituted alkenyl.

[0036] In some embodiments of the application, the polymer is subjected to self-polymerization under the action of a catalyst, or is subjected to crosslinking reaction by adding a polymerization monomer. In the embodiment of the application, the organic silicon polymer containing siloxane eight-membered ring is subjected to self-polymerization or crosslinking reaction by adding a polymerization monomer, which can form a compact network structure, further improve the flame-retardant performance, and effectively prolong the flame-retardant time.

[0037] In some embodiments of the present application, the polymerization monomer contains at least one of a silicon-hydrogen bond, a silicon-hydroxyl bond or a silicon-oxane bond. Preferably, the polymerization monomer contains at least two of a silicon-hydrogen bond, a silicon-hydroxyl bond or a silicon-oxane bond. Further preferably, the polymerization monomer is selected from at least one of phenyl tri(dimethyl siloxane silyl silane), diphenyl silicon-hydrogen or phenyl silane. In embodiments of the present application, the silicon-hydrogen bond, the silicon-hydroxyl bond or the silicon-oxane bond can add to the unsaturated hydrocarbon in the polymer, thereby cross-linking the plurality of organosilicon polymers into a network structure, facilitating the shaping process, while improving the flame retardant performance.

[0038] In some embodiments of the present application, the catalyst is selected from at least one of B(C6F5)3, Karstedt catalyst, platinum oxide, chloroplatinic acid, potassium hydroxide, a radical initiator, an organotin compound, anhydrous zinc chloride or a nickel metal.

[0039] Preferably, the ratio of the organosilicon polymer to the polymerization monomer is (4-6 g):(3-6 mmol).

[0040] Preferably, the ratio of the organosilicon polymer to the catalyst is (40-60):(0.02-0.04) by weight.

[0041] Preferably, the reaction temperature of the addition reaction is 50-100°C, and the reaction time is 2-3 hours.

[0042] A fireproof glass according to an embodiment of the present application, as shown in FIG. 1, comprises two glass substrates 1 and a flame-retardant coating 2 containing the flame-retardant material described above, which is sandwiched between the two glass substrates 1. Figure 1

[0043] The fireproof glass according to an embodiment of the present application uses an organosilicon polymer containing a silicon-octane ring, which significantly improves the fire resistance and heat shock resistance of the fireproof glass. The fireproof glass according to an embodiment of the present application can remain intact without breaking in a long-time burning environment.

[0044] Preferably, the thickness of the flame-retardant coating is 1-10 mm, preferably 1-5 mm. Since the organosilicon polymer according to an embodiment of the present application has excellent flame-retardant effect, the amount of the flame-retardant material can be reduced, the thickness of the flame-retardant coating can be reduced, the manufacturing cost of the fireproof glass can be reduced, and the use effect of the glass can be improved.

[0045] The present application will be described in detail below with reference to the embodiments.

[0046] Embodiment 1

[0047] ​An organic silicon polymer having a general formula shown in formula I is prepared by the method disclosed in the preparation method of embodiment 10 of the specification of patent CN107759791A, wherein R1, R2, R4, R5, R6, R7 are methyl, R3 is phenyl, R8 is vinyl, m = 37, n = 0, and the prepared organic silicon polymer is recorded as I-1.

[0048] Preparation of cross-linked organic silicon polymer G1: 40 g of organic silicon polymer I-1, 10.12 g (30 mmol) of phenyl tris(dimethyl siloxane silyl) and 20 mg of Karstedt catalyst are uniformly mixed, and addition reaction is carried out at 60°C for 3 h.

[0049] The cross-linked organic silicon polymer G1 prepared in this embodiment is coated between two layers of glass substrates, and the coating thickness is 2 mm.

[0050]

[0051] Example 2

[0052] The same method as in example 1, except that the preparation method of the cross-linked organic silicon polymer is as follows: 60 g of organic silicon polymer I-1, 6.48 g (60 mmol) of phenyl silane and 40 mg of chloroplatinic acid catalyst are uniformly mixed, and addition reaction is carried out at 60°C for 2 h to prepare the cross-linked organic silicon polymer G2.

[0053] The cross-linked organic silicon polymer G2 prepared in this embodiment is coated between two layers of glass substrates, and the coating thickness is 2 mm.

[0054] Example 3

[0055] An organic silicon polymer having a general formula shown in formula I is prepared by the method disclosed in the preparation method of embodiment 10 of the specification of patent CN107759791A, wherein R1, R2, R4, R5, R6, R7 are methyl, R3 is phenyl, R8 is vinyl, m = 120, n = 0, and the prepared organic silicon polymer is recorded as I-3.

[0056] Preparation of self-polymerized organic silicon polymer G3: 40 g of organic silicon polymer I-3 and 200 mg of AIBN catalyst are uniformly mixed, and addition reaction is carried out at 100°C for 8 h to prepare the cross-linked organic silicon polymer G3.

[0057] The self-polymerized organic silicon polymer G3 prepared in this embodiment is coated between two layers of glass substrates, and the coating thickness is 2 mm.

[0058] Example 4

[0059] An organic silicon polymer having a general formula shown in formula I is prepared by the method disclosed in the specification of patent CN107759791A, wherein R1, R2, R4, R5, R6, R7 are methyl, R3 is hydroxyl, R8 is ethoxyl, m = 120, n = 0, and the prepared organic silicon polymer is recorded as I-4.

[0060] A self-polymerized organic silicon polymer G4 is prepared: 40 g of the organic silicon polymer I-4 and 200 mg of stannous octoate are uniformly mixed, and addition reaction is carried out at 80°C for 10 h; the crosslinked organic silicon polymer G4 is prepared. The self-polymerized organic silicon polymer G4 prepared in this example is coated between two glass substrates, and the coating thickness is 2 mm.

[0061] Example 5

[0062] An organic silicon polymer having a general formula shown in formula I is prepared by the method disclosed in the specification of patent CN107759791A, wherein R1, R2, R4, R5, R6, R7 are methyl, R3 is ethenyl, R8 is phenyl, m = 62, n = 0, and the prepared organic silicon polymer is recorded as I-5.

[0063] A crosslinked organic silicon polymer G5 is prepared: 40 g of the organic silicon polymer I-5, 10.12 g (30 mmol) of phenyltris(dimethylsiloxylsilane) and 20 mg of Karstedt catalyst are uniformly mixed, and addition reaction is carried out at 60°C for 3 h.

[0064] The crosslinked organic silicon polymer G5 prepared in this example is coated between two glass substrates, and the coating thickness is 2 mm.

[0065] Example 6

[0066] The same method as that of example 1 is adopted, except that in the organic silicon polymer having a general formula shown in formula I, R1, R2, R4, R5, R6, R7 are methyl, R3 is phenyl, R8 is phenyl, m = 555, n = 0, and the preparation method adopts the method disclosed in the specification of patent CN107759791A, and the prepared organic silicon polymer is recorded as I-6.

[0067] The organic silicon polymer I-6 prepared in this example is coated between two glass substrates, and the coating thickness is 2 mm.

[0068] Example 7

[0069] The same method as that of example 1 is adopted, except that m = 80000, n = 0, and the prepared organic silicon polymer is recorded as I-7. The prepared crosslinked organic silicon polymer is recorded as G7.

[0070] The cross-linked silicone polymer G7 prepared in this example was coated between two glass substrates with a coating thickness of 2 mm.

[0071] Example 8

[0072] The same method as in Example 1, except that the polymerization monomer is dimethylphenylsilane, and the cross-linked silicone polymer prepared is denoted as G8.

[0073] The cross-linked silicone polymer G8 prepared in Example 8 was coated between two glass substrates with a coating thickness of 2 mm.

[0074] Example 9

[0075] The same method as in Example 1, except that m = 1000000, and the silicone polymer prepared is denoted as I-9. The cross-linked silicone polymer prepared is denoted as G9.

[0076] The cross-linked silicone polymer G9 prepared in Example 8 was coated between two glass substrates with a coating thickness of 2 mm.

[0077] Example 10

[0078] A silicone polymer having the general formula shown in Formula I was prepared using the method disclosed in the specification of patent CN107759791A, wherein R1, R2, R4, R5, R6, R7 are methyl, R3 is vinyl, R8 is dodecyl, m = 20, n = 2, and the silicone polymer prepared is denoted as I-10.

[0079] Preparation of cross-linked silicone polymer G10: the silicone polymer I-10 40 g, phenyl tris(dimethylsiloxyl silane) 10.12 g, and Karstedt catalyst 20 mg were mixed uniformly, and addition reaction was carried out at 60°C for 3 h;

[0080] The cross-linked silicone polymer G10 prepared in this example was coated between two glass substrates with a coating thickness of 2 mm.

[0081] Example 11

[0082] A silicone polymer having the general formula shown in Formula I was prepared using the method disclosed in the specification of patent CN107759791A, wherein R1, R2, R4, R5, R6, R7 are methyl, R3 is methyl, R8 is dodecyl, m = 40, n = 2, and the silicone polymer prepared is denoted as I-11.

[0083] Preparation of cross-linked silicone polymer G11: the silicone polymer I-11 40 g, potassium hydroxide 4 g, emulsifier dodecyl dimethyl bromide 0.5 g, and addition reaction was carried out at 80°C for 4 h.

[0084] The crosslinked silicone polymer G11 prepared in this example was coated between two glass substrates, and the coating thickness was 2 mm.

[0085] Example 12

[0086] The method for preparing the fireproof glass was the same as that of Example 1, except that the silicone polymer I-1 was coated between two glass substrates in the fireproof glass.

[0087] Example 13

[0088] The method for preparing the fireproof glass was the same as that of Example 3, except that the silicone polymer I-3 was coated between two glass substrates in the fireproof glass.

[0089] Comparative Example 1

[0090] The method for preparing the fireproof glass was the same as that of Example 1, except that the silicone adhesive of Dow Corning 2005 was used instead of the crosslinked silicone polymer of Example 1 in the fireproof glass.

[0091] Comparative Example 2

[0092] The method for preparing the fireproof glass was the same as that of Example 1, except that the crosslinked silicone polymer of Dow Corning 184 was used instead of that of Example 1 in the fireproof glass.

[0093] The fire retardant materials in the above examples and comparative examples were tested for the fire retardant grade according to the UL94 Fire Retardant Grade Standard, and the sample thickness was 1 mm; according to the test method of GB2409-84, the fire retardant test was performed on 5 groups of samples of each example or comparative example, and the fire retardant test was performed twice on each group of samples, and the two extinguishing times were t1 and t2, respectively, and the cumulative time of the 5 groups of samples was tf. The test results of each example and comparative example are shown in Table 1.

[0094] Table 1

[0095]

[0096] From the above tests, it can be seen that the fire retardant materials of the examples have excellent fire retardant properties, and especially the silicone polymers after self-polymerization or crosslinking reaction, the fire retardant properties are improved.

[0097] The fire resistance test was performed on the glass prepared in the above examples and comparative examples, and the test method was to place the glass sample at an angle of 90 degrees Celsius on the butane flame for burning, and the fire resistance test was performed, and the test results are shown in Table 2.

[0098] Table 2

[0099] Group Test time Fire resistance Thermal shock resistance Example 1 180 min Glass did not burn through Glass did not break Example 2 160 min Glass did not burn through Glass did not break Example 3 160 min Glass did not burn through Glass did not break Example 4 120 min Glass did not burn through Glass did not break Example 5 150 min Glass did not burn through Glass did not break Example 6 60 min Glass did not burn through Glass did not break Example 7 220 min Glass did not burn through Glass did not break Example 8 80 min Glass did not burn through Glass did not break Example 9 280 min Glass did not burn through Glass did not break Example 10 130 min Glass did not burn through Glass did not break Example 11 120 min Glass did not burn through Glass did not break Example 12 60 min Glass did not burn through Glass did not break Example 13 80 min Glass did not burn through Glass did not break Comparative Example 1 20 min Glass burned, coating burned Glass broke Comparative Example 2 30 min Glass burned, coating burned Glass broke

[0100] From the above results, it can be seen that the fireproof glass of the embodiments of the present application has excellent fire resistance and heat shock resistance, and the burning time can basically reach more than one hour, the glass is not burned through, and is not broken, especially in Example 1, the organic silicon polymer is cross-linked by using the polymeric monomer phenyl tris(dimethylsiloxane silyl), the burning time can reach 180 minutes, the glass is not burned through, and is not broken, the fireproof performance is excellent, compared with the organic polymer of Example 10 which is not cross-linked, the burning time is greatly prolonged. In Example 7, compared with Example 1, the value of m in the organic silicon polymer is increased, m=80000 is used, and the burning time is further improved, after 220 minutes of burning test, the glass is not burned through, and is not broken, and the performance of the fireproof glass is significantly improved. In the embodiments of the present application, the organic silicon polymer containing siloxane octacycle is applied in the fire-retardant material, and the fire-retardant performance of the fire-retardant material can be effectively improved, especially in the fireproof glass, the fireproof glass can not be broken under long-time burning, and the glass is kept intact.

[0101] In the present application, the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. mean that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. In addition, the skilled in the art can combine and combine the different embodiments or examples described in the present specification and the features of the different embodiments or examples without contradiction.

[0102] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limiting the present application, and the ordinary skilled in the art can make changes, modifications, replacements and variations to the above embodiments within the scope of the present application.

Claims

1. A fire resistant glass, characterized in that The application relates to a glass substrate and a fire-retardant coating, wherein the fire-retardant coating comprises a fire-retardant material, the fire-retardant material is prepared by self-polymerization of a siloxane octamer-containing organic silicon polymer under the action of a catalyst or cross-linking reaction of a polymerization monomer, and the polymer comprises a general structure shown in formula I. R1, R2, R4, R5, R6 and R7 are each independently selected from at least one of optionally substituted alkyl, optionally substituted cycloalkyl, optionally substituted heterocyclyl, optionally substituted phenyl and optionally substituted heteroaryl. R3 and R8 are each independently selected from at least one of optionally substituted alkyl, optionally substituted alkenyl, optionally substituted cycloalkenyl, optionally substituted heterocyclyl, optionally substituted aryl, optionally substituted heteroaryl and optionally substituted cyclohexyl. m is independently an arbitrary value between 2 and 3000000, and n is independently an arbitrary value between 0 and 3000000.

2. The fire protective glazing of claim 1, wherein, m is independently an arbitrary value between 30000 and 3000000.

3. The fire protective glazing of claim 1, wherein, At least one of R1-R8 is selected from optionally substituted aryl.

4. The fire protective glazing of claim 3, wherein, At least one of R3 and R8 is selected from optionally substituted aryl.

5. The fire protective glazing of claim 1, wherein, At least one of R3 and R8 is selected from optionally substituted alkenyl.

6. The fire protective glazing of claim 1, wherein, The polymerization monomer contains at least one of a silicon-hydrogen bond, a silicon-hydroxyl bond or a siloxane bond.

7. The fire protective glazing of claim 6, wherein, The polymerization monomer contains at least two silicon-hydrogen bonds, silicon-hydroxyl bonds or siloxane bonds.

8. The fire protective glazing of claim 6, wherein, The polymerization monomer is selected from at least one of phenyl tri(dimethyl siloxane silyl silane), diphenyl silane or phenyl silane.

9. The fire protective glazing of claim 1, wherein, The catalyst is selected from at least one of B(C6F5)3, Karstedt catalyst, platinum oxide, chloroplatinic acid, potassium hydroxide, a free radical initiator, an organic tin compound, anhydrous zinc chloride or a nickel metal.

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