CN103059338B - Polymerizable organic strong acid/sulfuric acid composite curing agent and its foamable phenolic resin composition - Google Patents

Abstract

The invention discloses a polymerizable organic strong acid / sulfuric acid composite curing agent and a foamable phenolic resin combination thereof. The combination comprises 100 parts of liquid A-stage phenolic resin, 7-9 parts of foaming agents, 2-6 parts of foam stabilizer, and 6-10 parts of polymerizable organic strong acid / sulfuric acid composite curing agents. The polymerizable organic strong acid / sulfuric acid composite curing agents are obtained through phenol or metacresol sulfonated in slightly excessive concentrated sulfuric acid, postprocessing processes of separation and the like are not needed, preparation processes are simple, and cost in low. The polymerizable organic strong acid / sulfuric acid composite curing agent can be chemically bonded with phenolic resin and directly brought in structure of foams, the polymerizable organic strong acid / sulfuric acid composite curing agent is not easy to permeate, small in corrosivity of base materials due to the fact that the potential of hydrogen (PH) value of the obtained foams reaches up to 5.8, rapid in foaming speed, and free from foam collapse and foam contraction.

Description

Polymerizable organic strong acid/sulfuric acid composite curing agent and its foamable phenolic resin composition

technical field

The invention relates to a polymerizable organic strong acid/sulfuric acid composite curing agent and a foamable phenolic resin composition thereof.

Background technique

Polymer foams are used as thermal insulation materials because of their porosity, light weight, and low heat transfer coefficient. Several polymer foam materials commonly used at present include polyurethane foam, polystyrene foam, polyethylene foam, and phenolic resin foam. Among them, although polyurethane, polystyrene, and polyethylene foam have good thermal insulation effect and high strength, they all have disadvantages such as low heat resistance temperature, easy to burn, easy to drip when burned, and large amount of smoke, making them especially suitable for practical applications. It is limited in the application of high temperature pipeline insulation, construction and other aspects. The phenolic foam material not only has a good heat preservation effect, but also has excellent heat resistance, and the service temperature can reach 250°C. What's more valuable is that it has excellent combustion resistance, self-extinguishing, small amount of smoke when burning, no dripping in case of fire, low smoke and low toxicity, flame penetration resistance, etc. Therefore, it has a unique position in the field of thermal insulation, and the research and development in developed countries is quite active. Phenolic foam is preferred as thermal insulation material in designated architectural designs in Europe, America and the Middle East.

Phenolic foam material is a thermosetting closed-cell foam material processed with liquid resole phenolic resin as the main raw material, foaming agent, foam stabilizer, curing agent and other additives. The expandable phenolic resin undergoes a cross-linking reaction at a certain temperature and is triggered by the curing agent, and at the same time releases a large amount of heat, which promotes the gasification of the low-boiling foaming agent, and forms a microcellular structure under the action of the foam stabilizer and is absorbed. The resin is fixed to obtain a phenolic foam with a uniform cell structure.

The curing agent that can trigger the curing reaction of liquid resole phenolic resin is generally an inorganic acid such as sulfuric acid, phosphoric acid, hydrobromic acid, boric acid, etc., or an organic acid such as benzenesulfonic acid, p-toluenesulfonic acid, acetic acid, naphthalenesulfonic acid, etc. . Inorganic acids have the characteristics of short induction period, fast foaming speed, complete curing, not easy to cause foam collapse, and good dimensional stability; while organic acids have a longer induction period, slow foaming, and are prone to foam collapse and shrinkage. And so on. There are also inorganic acids and organic acids used in combination to improve their effects. However, whether it is an organic acid, an inorganic acid or a compound thereof as a curing agent, the curing agent still exists in the foam in a free state after the foam molding of the phenolic resin composition. The pH value of the foam is low, the acidity is large, and the free acidic substance It is easy to penetrate to the surface and cause strong corrosion to some substrates, thus limiting the application of phenolic foam in military, aerospace, construction and many other fields. For a long time, the corrosion of phenolic foam materials to substrates has been a hot spot of concern. To solve this problem, domestic and foreign scholars have carried out a series of researches.

US7605189 provides a preparation process of phenolic foam. The phenolic resin and thermally decomposed solid foaming agent are mixed uniformly by hot rollers, and then gel-like plates are prepared on a calender, and then heated to decompose the foaming agent into gas to form phenolic foam. body, and further heat-treated at 170°C to form a high-strength, light-weight and low-acid phenolic foam. This method utilizes self-condensation of methylol at high temperature to form a cross-linked structure without the use of an acidic curing agent, thereby avoiding the corrosion problem caused by the acidic curing agent, but this method has high requirements for equipment, complex processes, and difficult control. The curing temperature is high, the energy consumption is large, and the cost is high; WO9404604 provides a method of curing through phenolic resin, alkyl-alkoxyphenol surfactant and silanol copolymer surfactant, n-pentane, inorganic acid and aromatic Prepare phenolic foam with sulfonic acid, and then place the cured foam in NH3 at 63-71°C for 36 hours to neutralize the remaining acid in the reaction to reduce the acidity of the phenolic foam. However, this method needs to neutralize the prepared phenolic foam under NH3 environment for 36 hours, the production cycle is long, the process is complicated, and the production efficiency is low; A method for preparing phenolic foam from silicon and calcium carbonate, the phenolic foam produced by the method has low acidity and a pH of 6.0; CN101305034A and CN101305035A disclose a phenolic foam, the raw material ratio of which is: 100 parts of phenolic resin; blowing agent 1~20 parts; catalyst 5~25 parts; inorganic filler 1~20 parts; surfactant 1~6 parts. The catalyst is at least one of benzenesulfonic acid, p-toluenesulfonic acid, xylenesulfonic acid, naphthalenesulfonic acid, ethylbenzenesulfonic acid and phenolsulfonic acid; the inorganic filler is at least one of the following substances: metal oxides such as oxide Aluminum or zinc oxide; Metal powder such as zinc; Metal hydroxide such as aluminum hydroxide, magnesium hydroxide; Or metal carbonate such as magnesium carbonate, barium carbonate, calcium carbonate, zinc carbonate, the pH value of the phenolic foam prepared by this method is greater than or equal to 5. The above method is to slowly neutralize the remaining acid after phenolic foaming by adding one or more of basic inorganic metal powders, metal oxides, metal hydroxides, or metal carbonates to reduce phenolic foam. acidity, reducing its corrosiveness. However, only organic acid is used as the curing agent in the above method, and part of the curing agent has been consumed by the neutralizing agent in the mixing process before the phenolic resin is cured. To achieve the same foaming speed, it is necessary to greatly increase the amount of curing agent or even up to 25%; CN102675821A provides a preparation method of low-acid phenolic foam, its raw material ratio is: 100 parts of expandable phenolic resin; 2~8 parts of surfactant; 5~10 parts of foaming agent; 10 parts of neutralizing agent ~50 parts; 1~5 parts of acid absorbing agent; 10~20 parts of curing agent. The neutralizer is at least one of barium hydroxide, magnesium hydroxide, magnesium oxide, calcium oxide, calcium carbonate, etc.; the acid absorbing agent is glutaraldehyde-crosslinked amine-containing polymer particles, and the prepared phenolic foam has low acidity , pH is 5~6. This method is on the basis of CN101305034A, CN101305035A and JP2010285496, replaces part of inorganic neutralizer with organic alkali acid absorbing agent, can reduce the consumption to curing agent when mixing materials, reduces the consumption of curing agent, can drop to 20%, but The so-called acid absorber is essentially a neutralizer, but it is an organic weak base, which reacts slowly with the curing agent, which can reduce the consumption of the curing agent during the mixing process, but it does not solve the problem of the amount of acid curing agent. It is a big problem, and the apparent density of the phenolic foam prepared after adding inorganic neutralizer or acid absorbing agent in the above method increases, and the safety and thermal insulation performance decrease.

Contents of the invention

One of the objectives of the present invention is to provide a polymerizable organic strong acid/sulfuric acid composite curing agent.

The second object of the present invention is to provide a foamable phenolic resin composition with low acidity and low corrosion.

The present invention uses a compound of a polymerizable organic strong acid and a small amount of sulfuric acid as a curing agent. The polymerizable organic strong acid is phenol sulfonic acid or m-cresol sulfonic acid, which is directly sulfonated by phenol or m-cresol in slightly excessive concentrated sulfuric acid. After the sulfonation is completed, some polymerizable diluents are added to promote dissolution, so as to ensure that the composite curing agent is homogeneous and convenient to use. Phenolsulfonic acid and m-cresolsulfonic acid have the following structures:

                    

Phenolsulfonic acid m-cresolsulfonic acid

When it is used as a liquid phenolic resin curing agent, it can react with phenolic resin as follows:

The acidic curing agent is chemically bonded in the phenolic resin structure to become an integral part of the foam, and will not penetrate and migrate to the surface of the foam, so that the pH value of the prepared phenolic foam can reach 5.8, which greatly reduces the acidity of the substrate. corrosion. The product obtained by the direct sulfonation process in excess concentrated sulfuric acid is a mixture of phenolsulfonic acid or m-cresolsulfonic acid and a small amount of sulfuric acid. The excess sulfuric acid does not need to be separated, and it exists in the curing agent just to make up for the organic acid curing agent. The induction period is longer during foaming, the curing speed is slower, and it is easy to collapse or shrink.

According to the above mechanism, the present invention adopts the following technical solutions:

A polymerizable organic strong acid/sulfuric acid composite curing agent is characterized in that the curing agent is composed of phenolsulfonic acid or m-cresolsulfonic acid, sulfuric acid and a diluent, wherein the molar ratio of phenolsulfonic acid or m-cresolsulfonic acid to sulfuric acid 1:0.1-0.3; the diluent is at least one of ethylene glycol, diethylene glycol, and triethylene glycol, and its dosage accounts for 20%-35% of the total mass of the curing agent.

A method for preparing the above-mentioned polymerizable organic strong acid/sulfuric acid composite curing agent, characterized in that the specific steps of the method are: preheating phenol or m-cresol to 75-85°C, slowly adding concentrated sulfuric acid within 1 hour under stirring , after adding, continue to react for 2.5～3.5 hours; add diluent again, cool and discharge after stirring, obtain polymerizable organic strong acid/sulfuric acid composite curing agent; the mol ratio of described phenol or m-cresol and sulfuric acid is 1: 1.1～1:1.3.

A kind of foamable phenolic resin composition, by above-mentioned polymerizable organic strong acid/sulfuric acid composite curing agent as curing agent, it is characterized in that the composition of this composition and its mass parts are:

Liquid resole phenolic resin 100 parts;

Foaming agent 7~9 parts;

Foam stabilizer 2~6 parts;

Polymerizable organic strong acid/sulfuric acid composite curing agent 6~10 parts.

The above-mentioned liquid resole phenolic resin has a solid content of 80-85% and a viscosity of 2000-5000mpa.s at 25°C.

Above-mentioned whipping agent is a kind of in low boiling point solvent n-pentane, methylene chloride, sherwood oil.

The above-mentioned foam stabilizer is at least one of Tween surfactant, silicone surfactant or Spann surfactant.

The above-mentioned Tween surfactant is at least one of Tween-80, Tween-60 and Tween-20.

The silicone surfactant mentioned above is at least one of DC-193, DC-198 and DC-2525.

The above-mentioned Span-like surfactants are: at least one of Span-80, Span-60 and Span-20.

The organic strong acid in the polymerizable organic strong acid/sulfuric acid composite curing agent in the composition of the present invention may be phenolsulfonic acid or m-cresolsulfonic acid. During the foaming process of phenolic resin, the active points on phenolsulfonic acid or m-cresolsulfonic acid can be condensed with the methylol group on resole phenolic resin, directly introduced into the foam structure, and become a part of the foam. Instead of existing in the foam in the form of free acid, it penetrates and migrates to the surface of the foam, which is corrosive to the substrate. Its reaction scheme is as follows:

In the above-mentioned preparation steps, the ratio of phenol or m-cresol to sulfuric acid is 1:1.1 ~ 1:1.3. Slightly excess sulfuric acid, after the sulfonation reaction, the excess sulfuric acid and phenolsulfonic acid or m-cresolsulfonic acid in the system constitute a polymerizable organic strong acid/sulfuric acid composite curing agent. When there is too much sulfuric acid, there will be more free acid in the foam after foaming, and the pH value will be low; when the sulfuric acid is too little, there will be less inorganic strong acid in the composite curing agent, which will slow down the curing speed during curing, and even cause foam collapse. The optimal ratio of phenol or m-cresol to sulfuric acid is 1:1.15~1:1.25.

above steps The diluent is one of ethylene glycol, diethylene glycol, and triethylene glycol or a compound thereof, and the amount thereof accounts for 20% to 35% of the total curing agent. The diluent acts as a solubilizer in the system to ensure that the composite curing agent remains homogeneous for easy use. At the same time, the diluent used can participate in the reaction, become a part of the foam structure, and play a role in toughening the foam. Its reaction formula is as follows:

Compared with the traditional technology, the present invention has the following prominent substantive advantages and significant progress:

1. Using a polymerizable organic strong acid/sulfuric acid composite curing agent, when foaming, the curing agent is directly connected to the foam with chemical bonds and introduced into the foam structure without osmotic migration. The pH value of the prepared foam can reach as high as 5.8. The corrosion of the base material is small, and the foaming speed is fast, and there is no foam collapse phenomenon.

2. Phenol or m-cresol is sulfonated in a slight excess of concentrated sulfuric acid, and the product does not need to undergo post-processing steps such as separation. Excess sulfuric acid and the generated phenolsulfonic acid or m-cresolsulfonic acid can be directly produced by diluent assisted dissolution. Polymerized organic strong acid/sulfuric acid composite curing agent has simple process, low cost and strong operability.

3. The present invention does not add any inorganic neutralizer or acid absorbing agent, and the amount of curing agent used is only 6-10%. The prepared phenolic foam has low apparent density, good heat preservation effect and safety.

Detailed ways

The following examples are to further illustrate the present invention, but not to limit the scope of the present invention.

Example 1:

1. Add 141g of phenol into the reactor and preheat to 80°C; 165g (98%) concentrated sulfuric acid was slowly added to the reaction vessel within 1 hour under stirring, and continued to react for 3 hours after adding; Add 116g of ethylene glycol, stir evenly, then cool and discharge to obtain curing agent C-1.

2. Weigh 90g of liquid resole phenolic resin, 2.7g of DC-193, 8.1g of methylene chloride, 7.2g of curing agent C-1 in a plastic beaker. In a 200*200*40 steel mould, put the mold into a 60-75°C oven to foam for 20 minutes, cool and demould, and obtain a phenolic foam with a uniform cell structure and an apparent density of 0.043g/cm ³ . The rate is greater than 92%, and the pH value is 5.8.

Example 2:

1. Add 141g of phenol into the reactor and preheat to 80°C; Slowly add 180g (98%) concentrated sulfuric acid to the reaction vessel under stirring within 1 hour, and continue to react for 3 hours after adding; Add 80g of diethylene glycol, stir evenly, then cool and discharge to obtain curing agent C-2.

2. Weigh 90g of liquid resole phenolic resin, 2.7g of DC-193, 8.1g of methylene chloride, 6.3g of curing agent C-2 in a plastic beaker. In a 200*200*40 steel mould, put the mold into a 60-75°C oven to foam for 20 minutes, cool and demould, and obtain a phenolic foam with a uniform cell structure and an apparent density of 0.041g/cm ³ . The rate is above 92%, and the pH value is 5.6.

Example 3:

1. Add 162g m-cresol into the reactor and preheat to 80°C; 172.5g (98%) concentrated sulfuric acid was slowly added to the reaction vessel within 1 hour under stirring, and the reaction was continued for 3 hours after adding; Add 175 g of triethylene glycol compound, stir evenly, then cool and discharge to obtain curing agent C-3.

2. Weigh 90g of liquid resole phenolic resin, 3.6g of Tween-80, 6.3g of n-pentane, 7.8g of curing agent C-3 in a plastic beaker. Put the mold into a 200*200*40 steel mould, put the mold into a 60-75°C oven to foam for 20 minutes, cool and demould, and obtain a phenolic foam with a uniform cell structure and an apparent density of 0.045g/cm ³ . The porosity is 93%, and the pH value is 5.8.

Example 4:

1. Add 162g m-cresol into the reactor and preheat to 80°C; 195g (98%) concentrated sulfuric acid was slowly added to the reaction vessel within 1 hour under stirring, and the reaction was continued for 3 hours after adding; Add 118g of the compound of ethylene glycol and triethylene glycol, stir evenly, then cool and discharge to obtain curing agent C-4.

2. Weigh 90g of liquid resole phenolic resin, 3.6g of Tween-80, 6.3g of n-pentane, 6.7g of curing agent C-4 in a plastic beaker. Put the mold into a 200*200*40 steel mould, put the mold into a 60-75°C oven to foam for 20 minutes, cool and demould, and obtain a phenolic foam with a uniform cell structure and an apparent density of 0.042g/cm ³ . The porosity is greater than 92%, and the pH value is 5.5.

Claims (8)

1. A polymerizable organic strong acid/sulfuric acid composite curing agent is characterized in that this curing agent is made up of phenolsulfonic acid or m-cresolsulfonic acid, sulfuric acid and diluent, wherein phenolsulfonic acid or m-cresolsulfonic acid and sulfuric acid The molar ratio is 1:0.1-0.3; the diluent is at least one of ethylene glycol, diethylene glycol, and triethylene glycol, and its consumption accounts for 20%-35% of the total mass of the curing agent. %; The phenolsulfonic acid or m-cresolsulfonic acid is prepared by the following method: preheat phenol or m-cresol to 75-85°C, slowly add concentrated sulfuric acid within 1 hour under stirring, and continue the reaction after adding 2.5-3.5 hours; the molar ratio of phenol or m-cresol to sulfuric acid is 1:1.1-1:1.3. 2. a foamable phenolic resin composition, is curing agent by polymerizable organic strong acid/sulfuric acid composite curing agent according to claim 1, it is characterized in that the composition and mass parts thereof of this composition are: Liquid resole phenolic resin 100 parts; Foaming agent 7~9 parts; Foam stabilizer 2~6 parts; Polymerizable organic strong acid/sulfuric acid composite curing agent 6~10 parts. 3. The composition according to claim 2, characterized in that the solid content of the liquid resole phenolic resin is 80-85%, and the viscosity at 25° C. is 2000-5000 mPa.s. 4. composition according to claim 2 is characterized in that described blowing agent is the one in low-boiling point solvent n-pentane, methylene dichloride, sherwood oil. 5. The composition according to claim 2, characterized in that the foam stabilizer is at least one of Tween surfactants, silicone surfactants or Spann surfactants. 6. The composition according to claim 5, characterized in that the Tween surfactant is at least one of Tween-80, Tween-60 and Tween-20. 7. The composition according to claim 5, characterized in that the silicone surfactant is at least one of DC-193, DC-198, and DC-2525. 8. The composition according to claim 5, characterized in that said Span-like surfactant is: at least one of Span-80, Span-60, and Span-20.