CN113307906B

CN113307906B - Method for producing a high internal phase emulsion foam without hydrophilic post-treatment, foam and use thereof

Info

Publication number: CN113307906B
Application number: CN202110503054.XA
Authority: CN
Inventors: 尉晓丽; 田云; 纪学顺
Original assignee: Wanhua Chemical Group Co Ltd
Current assignee: Wanhua Chemical Group Co Ltd
Priority date: 2021-05-10
Filing date: 2021-05-10
Publication date: 2022-07-12
Anticipated expiration: 2041-05-10
Also published as: CN113307906A

Abstract

The invention relates to a preparation method of high internal phase emulsion foam without hydrophilic post-treatment, a foam material and application thereof. The method of the invention not only saves the step of hydrophilizing the foam by using a surfactant and/or a hydrophilizing reagent salt solution in the later period, but also can reduce the addition amount of the nonionic emulsifier in the traditional high internal phase emulsion, and finally can obtain the foam material with multiple hydrophilicities, safe use and good absorption performance.

Description

Method for producing a high internal phase emulsion foam without hydrophilic post-treatment, foam and use thereof

Technical Field

The invention relates to the technical field of foam material preparation, in particular to a preparation method of a foam material which is obtained by polymerizing a high internal phase emulsion and still has multiple hydrophilicities without hydrophilic post-treatment, the foam material and application thereof.

Background

Porous foams prepared from High Internal Phase Emulsions (HIPEs) have a variety of applications, such as sound insulation, thermal insulation, disposable absorbent articles, filters, and pharmaceutical carriers, among others. HIPE is an ultra-concentrated system (water-in-oil or oil-in-water) containing a large amount of the internal phase, i.e. the dispersed phase, with a volume fraction of the dispersed phase exceeding 74%, resulting in deformation of the droplets of the dispersed phase into polyhedra, which are separated by thin films of the continuous phase. When the dispersed phase is aqueous phase droplets and the continuous phase is polymerizable monomer, the monomer polymerizes into cell walls after polymerization, and a porous structure such as a foam can be formed, wherein the cell size of the porous structure is determined by the size distribution of the aqueous phase droplets.

In the prior art, the foam material prepared by high internal phase emulsion and used as a disposable sanitary absorbent product is determined by the structure of the polymer of the foam material if the foam is not subjected to hydrophilization treatment after solidification and washing, the foam is hydrophobic, and the hydrophobic foam material is not beneficial to absorbing urine, blood or menstrual blood-containing fluid and can cause the condition of slow absorption and leakage, so the hydrophilic treatment is necessary for the foam material.

The prior known foam hydrophilic treatment method is that a surfactant, a hydrated inorganic salt or a mixture of the surfactant and the hydrated inorganic salt are used for treating foam, and after one or more times of hydrophilic treatment, the required foam material is obtained by drying, although the absorption performance of the obtained foam material compared with hydrophilic fluid such as urine, blood and the like can meet the requirement, the hydrophilic treatment process is complicated and needs to be carried out at a certain temperature, and the method relates to multiple times of washing and extrusion treatment, is not beneficial to continuous production process, also increases production energy consumption, and the residual hydrophilic surfactant can cause sticky hand feeling and influence the subsequent drying speed, thereby influencing the dryness of the surface of the foam material; in addition, the selected hydrophilic surfactant must be a skin-safe and non-irritating ingredient to prevent irritation of the skin contact area by the surfactant migrating during use, which also limits the choice of hydrophilic treatment agents.

If water-soluble surfactants are selected to treat the foam, although the short-term hydrophilicity of the foam can be significantly improved, the water-soluble surfactants are dissolved in hydrophilic fluid and released from the foam into the fluid, so that the surface tension of the fluid is changed, and the absorption of the fluid by the foam is influenced; on the other hand, the content of the hydrophilic fluid in the foam is reduced, so that the hydrophilicity of the foam is reduced for many times, and the hydrophilicity of the foam is obviously reduced after the hydrophilic fluid is added for many times in an actual test, so that the risk of leakage in actual use is increased.

If the foam is treated with water-insoluble surfactants, as described in patents CN1070924A, CN1228016A, CN1177359A, using surfactants such as sorbitan fatty acid esters or polyglycerin fatty acid esters, it has been found experimentally that the multiple hydrophilicity of the foam is improved well by treating the foam with such low water-soluble surfactants, but these poor water-soluble surfactants remain on the surface of the foam resulting in a sticky feel, insufficient dryness and an adverse effect on the rate of subsequent drying treatment of the foam.

If treated with a hydrophilizing agent salt solution, such as a metal halide salt (calcium halide, magnesium halide, sodium halide, etc.), it has been found that absorption of a blood-containing fluid having a relatively high viscosity (e.g., menstrual fluid) is affected when the absorbent foam contains a relatively high content of hydrated inorganic salts, resulting in a greatly reduced absorption rate, which increases the probability of liquid leakage in actual use. In addition, these water-soluble inorganic salts are dissolved in aqueous fluid during use and lost, resulting in deterioration of the hydrophilicity of the foam several times, so that the hydrophilicity of the absorbent foam is obtained by a reasonably effective hydrophilic treatment in consideration of the above factors.

Disclosure of Invention

In order to solve the problems of the prior art, the invention aims to provide a preparation method for preparing a high internal phase emulsion foam material which has multiple hydrophilicities and does not need hydrophilic post-treatment, and the method omits the hydrophilic post-treatment process and is simple and easy to implement.

It is a further object of the present invention to provide high internal phase emulsion foams having multiple hydrophilicities prepared by the foregoing process without the need for hydrophilic post-treatments.

It is a further object of this invention to use such high internal phase emulsion foams that are multiple hydrophilic and do not require hydrophilic post-treatment.

In order to achieve the above purpose, the invention adopts the following technical scheme:

a method of making a high internal phase emulsion foam without hydrophilic post-treatment comprising the steps of:

1) preparing a water-in-oil emulsion comprising an oil phase comprising, based on the total weight of the oil phase:

a) from 70% to 99% by weight of a substantially water-insoluble monomer component;

b) 1-30% by weight of an emulsifier component soluble in the oil phase and capable of forming a stable water-in-oil emulsion;

2) curing the water-in-oil emulsion to form a foam; preferably, the curing is carried out by putting the mixture into an oven, a water bath or a UV light irradiation mode;

3) and washing, dehydrating and drying the solidified foam to obtain the high internal phase emulsion foam material without hydrophilic post-treatment.

In a particular embodiment, the aqueous phase of the water-in-oil emulsion comprises:

a) 1-10 wt% of water-soluble electrolyte based on the weight of the aqueous phase, wherein the electrolyte is inorganic water-soluble salt; preferably, the inorganic water-soluble salt is selected from monovalent, divalent inorganic salts of alkali metals and halide or sulfate salts of alkali metals;

b) 0-6% by weight of water-soluble sulfonate or sulfate containing allyl or acrylamide groups based on the total weight of monomers in the oil phase; preferably, the water-soluble sulfonate or sulfate containing allyl or acrylamide groups is selected from at least one of sodium allyl ether hydroxypropyl sulfonate, sodium 2-acrylamido-2-methylpropane sulfonate, sodium p-styrene sulfonate and sodium 2-acrylamido-2-methylpropane sulfonate;

c) based on the total weight of the monomers of the oil phase, 1-15% of water-soluble initiator based on the total weight of the monomers; preferably, the initiator is selected from persulfates, more preferably at least any one of potassium persulfate, sodium persulfate, or ammonium persulfate;

preferably, the weight ratio of the water phase volume to the oil phase of the water-in-oil emulsion is 10 mL-80 mL: 1g of the total weight of the composition.

In a particular embodiment, the monomer component in a) of the oil phase comprises:

i) from 60 to 95 weight percent, based on the total weight of monomers contained in the oil phase, of at least one substantially water-insoluble monofunctional comonomer; preferably, the monofunctional comonomer is selected from styrene, alkyl acrylates, alkyl methacrylates and mixtures thereof; more preferably, from 70% to 90% by weight of a monomer component selected from: acrylic acid C₄-C₁₈Alkyl esters, methacrylic acid C₄-C₁₈Alkyl ester esters, styrene, alkylstyrene, and mixtures thereof;

ii) 5 to 40 weight percent, based on the total weight of monomers contained in the oil phase, of at least one substantially water-insoluble polyfunctional crosslinking agent; preferably, the multifunctional crosslinking agent is selected from divinyl aromatics, diacrylates or dimethacrylates of polyols, and mixtures thereof; more preferably, from 10 to 30 weight percent of a multifunctional crosslinking agent selected from the group consisting of divinylbenzene, trivinylbenzene, divinyltoluene, divinylxylene, ethylene glycol dimethacrylate, 1, 6-hexanediol dimethacrylate, and mixtures thereof.

In a particular embodiment, said oil soluble emulsifier in b) of said oil phase comprises:

i) an oil-soluble polymerizable first emulsifier which accounts for at least 40% by weight of the emulsifier component; preferably, the polymerizable first emulsifier is an unsaturated fatty acid ester emulsifier containing a plurality of hydroxyl groups; more preferably, the oil-soluble polymerizable first emulsifier is an oil-soluble polymerizable first emulsifier having a weight percentage of not less than 50% based on the emulsifier component, the first emulsifier being selected from the group consisting of an acryloyl sorbitan fatty acid ester, an acryloyl polyglycerin fatty acid ester, an acryloyl polyol fatty acid ester or an acryloyl sucrose fatty acid ester, and a mixture thereof;

ii) an oil-soluble non-reactive second emulsifier present in an amount of at least 10% by weight of the emulsifier component; preferably, the emulsifier is soluble in the oil phase and is capable of forming a stable water-in-oil emulsion; more preferably, the emulsifier component is not less than 20% by weight of an oil-soluble non-reactive secondary emulsifier selected from the group consisting of glycerol fatty acid esters, polyglycerol fatty acid esters, (poly) glycerol succinic acid esters, sorbitan fatty acid esters, sucrose fatty acid esters or alkylphenol ethoxylates and mixtures thereof.

In a specific embodiment, the oil phase and water phase mixed emulsification temperature for preparing the water-in-oil emulsion in the step 1) is 40-80 ℃, and a stable water-in-oil emulsion is formed under the mixing shearing speed of 500-3000 rpm; preferably, the emulsified high internal phase emulsion can be stably placed at the temperature of 40-80 ℃ for more than 2 hours, and an anhydrous oil separation phenomenon is generated.

In a specific embodiment, the curing temperature of the water-in-oil emulsion in the step 2) is 55-150 ℃, and the curing time is not less than 8 hours.

In a specific embodiment, the high internal phase emulsion foam produced in step 3) without hydrophilic post-treatment has a final water content of less than 5% and a hydratable salt content of less than 0.1%.

In another aspect of the present invention, a high internal phase emulsion foam prepared by the foregoing method without hydrophilic post-treatment preferably has a foam number average cell diameter of 30 μm to 100 μm and a cell number average diameter between adjacent cells of less than 20 μm; more preferably, the Tg of the foam polymer is from-25 ℃ to 35 ℃.

In a specific embodiment, the foam has a vertical wicking speed of less than 13min (2cm absorption height), a soaking time of less than 40s, and an absorption speed of greater than 20g/g/min, using a standard synthetic fluid as the test fluid; preferably, the foam has a contact angle with the test liquid of less than 60 °, which does not increase after multiple injections of the test liquid, and is hydrophilic multiple times.

In a further aspect of the present invention, the use of the aforementioned high internal phase emulsion foam without hydrophilic post-treatment in sanitary absorbent articles, preferably baby diapers, adult incontinence articles, medical bandages or feminine napkins.

Compared with the prior art, the preparation method of the high internal phase emulsion foam material without hydrophilic post-treatment has the following beneficial effects:

the invention relates to a preparation method of a foam material with good multiple hydrophilicity, which utilizes a reaction type oil-soluble emulsifier synthesized in a laboratory in HIPE polymerization to obtain the foam material with good multiple hydrophilicity. The hydrophilic treatment method adopted in the prior published patent adopts a nonionic emulsifier solution with high HLB value or/and an electrolyte solution to carry out hydrophilic treatment on solidified foam, so that on one hand, the hydrophilic treatment process is complicated and time-consuming, the production cost is increased, on the other hand, the hydrophilic treatment mode endows the foam with hydrophilicity which has no long-term effect, and the hydrophilicity of the foam is reduced along with the loss of the emulsifier in a multi-liquid adding test. The preparation method of the invention not only omits the step of hydrophilization treatment on the foam by using a surfactant or a hydrophilization reagent salt solution or a mixture of the surfactant and the hydrophilization reagent salt solution in the later period, but also can reduce the addition amount of the nonionic emulsifier with high dosage in the traditional high internal phase emulsion, and finally can obtain the foam material with multiple hydrophilicities, safe use and good absorption performance.

Drawings

FIG. 1 is a photomicrograph (at 100X magnification) of a cross-section of the foam prepared in example 1;

FIG. 2 is a graph of an apparatus for testing the vertical wicking speed of the foam of the present invention;

FIG. 3 is a graphical representation of the contact angle test results after 1 addition of examples 1 (left) and comparative example 3 (right) of the present invention;

FIG. 4 is a graph showing the results of the contact angle test after 5 shots of liquid for example 1 (left) and comparative example 3 (right) according to the present invention.

Detailed Description

The following examples will further illustrate the method provided by the present invention in order to better understand the technical solution of the present invention, but the present invention is not limited to the listed examples, and should also include any other known modifications within the scope of the claims of the present invention.

A preparation method of a high inward emulsion foam material without hydrophilic post-treatment comprises the following specific preparation steps:

(1) an oil phase as a continuous phase containing monomers, cross-linking agents and emulsifiers is mixed with an aqueous phase as a dispersed phase containing initiators, stabilizers, electrolytes at a temperature of 40 ℃ to 80 ℃, preferably 40 ℃ to 70 ℃, more preferably 45 ℃ to 60 ℃ to form a stable high internal phase water-in-oil emulsion.

(2) The high internal phase emulsion formed is cured in a water bath or oven or under UV light conditions at a temperature of from 55 ℃ to 150 ℃, preferably from 55 ℃ to 90 ℃ for a period of from 8 to 24 hours.

(3) And washing and slicing the solidified foam, extruding and dehydrating the foam under certain pressure, and finally drying the foam in an oven at 60 ℃ for 3 hours.

Wherein, in the step (1), the mixing shear rate of the oil phase and the water phase is 500rpm to 3000rpm, such as but not limited to 500rpm, 800rpm, 1000rpm, 1250rpm, 1500rpm, 1750rpm, 2000rpm, 2250rpm, 2500rpm, 2750rpm, 3000rpm, more preferably, the mixing shear rate is 500rpm to 2000 rpm; the mass ratio of the water phase volume to the oil phase is 10 mL-80 mL: 1g, for example including but not limited to 15 mL: 1g, 20 mL: 1g, 25 mL: 1g, 30 mL: 1g, 35 mL: 1g, 40 mL: 1g, 45 mL: 1g, 50 mL: 1g, 55 mL: 1g, 60 mL: 1g, 65 mL: 1g, 70 mL: 1g, 75 mL: 1g of a compound; more preferably, the mass ratio of the volume of the aqueous phase to the mass of the oil phase is between 20 mL: 1 g-55 mL: 1g of the total weight of the composition.

In step (1), the substantially water-insoluble monomer component contained in the oil phase accounts for 70% to 99% of the total weight of the oil phase, including, but not limited to, 70%, 75%, 80%, 85%, 90%, 95%, preferably 70% to 90% of the total weight of the oil phase. The substantially water-insoluble monomer component refers to a monomer component that is slightly soluble, poorly soluble, or insoluble in water at 20 ℃.

Wherein the monomer component comprises: i) from 60 to 95 weight percent of at least one substantially water-insoluble monofunctional comonomer, based on the total weight of monomers contained in the oil phase; preferably, the monofunctional comonomer is selected from the group consisting of styrene, alkyl acrylates, alkyl methacrylates, aryl acrylates, and mixtures thereof; more preferably, from 70% to 90% by weight of a monomer component selected from: acrylic acid C₄-C₁₈Alkyl esters, methacrylic acid C₄-C₁₈Alkyl ester esters, styrene, alkylstyrene, and mixtures thereof. Such as butyl acrylate, isooctyl acrylate, n-octyl acrylate, n-hexyl acrylate, nonyl acrylate, decyl acrylate, isodecyl acrylate, dodecyl acrylate, tetradecyl acrylate, hexyl methacrylate, isooctyl methacrylate, decyl methacrylate, isodecyl methacrylate, dodecyl methacrylate, tetradecyl methacrylate, or octadecyl methacrylate; the monomer component may also contain water-insoluble comonomers such as vinyl chloride, isoprene or chloroprene.

ii) 5 to 40 weight percent, based on the total weight of monomers contained in the oil phase, of at least one substantially water-insoluble polyfunctional crosslinking agent; for example, including but not limited to 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40% by weight of the total monomers of at least one substantially water insoluble polyfunctional crosslinking agent selected from the group consisting of divinyl aromatics, diacrylates or dimethacrylates of polyols, and mixtures thereof; more preferably, 10 to 30 weight percent of a multifunctional crosslinking agent selected from any one of divinylbenzene, trivinylbenzene, divinyltoluene, divinylxylene, 1, 4-ethylene glycol dimethacrylate, 1, 6-hexanediol dimethacrylate, ethylene glycol dimethacrylate, hexanediol dimethacrylate, etc., or mixtures of these components, the crosslinking agent component being capable of providing the desired resiliency and strength to the foam.

In step (1), the oil phase comprises 1% to 30% by weight of an emulsifier component soluble in the oil phase and capable of forming a stable water-in-oil emulsion, including, for example, but not limited to, 1%, 3%, 5%, 8%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30% by weight of an emulsifier component soluble in the oil phase and capable of forming a stable water-in-oil emulsion, the oil-soluble emulsifier comprising at least 40% by weight of the emulsifier component of an oil-soluble polymerizable first emulsifier and at least 10% by weight of the emulsifier component of an oil-soluble non-reactive second emulsifier, including, but not limited to, 40% by weight of the emulsifier component of an oil-soluble polymerizable first emulsifier and 60% by weight of the emulsifier component of an oil-soluble non-reactive second emulsifier The second emulsifier is a soluble non-reactive second emulsifier, or 60 wt% of the first emulsifier and 40 wt% of the second emulsifier, or 90 wt% of the first emulsifier and 10 wt% of the second emulsifier.

Specifically, the polymerizable first emulsifier is an unsaturated fatty acid ester emulsifier containing a plurality of hydroxyl groups, and is selected from any one of acryloyl sorbitan stearate, acryloyl sorbitan monooleate, acryloyl pentaerythritol monostearate, acryloyl pentaerythritol monooleate, and acryloyl sucrose fatty acid monoester or a mixture of the components. The first emulsifier contains active groups capable of reacting with the monomer and can be grafted to a polymer molecular chain in a curing reaction, so that the first emulsifier can exist stably in washing and dehydration treatment at the later stage of foam, and therefore certain multiple hydrophilicity can be provided to the foam.

Wherein the oil-soluble non-reactive second emulsifierSelected from branched or straight chain C₁₆-C₂₄Fatty acid glycerides, branched or straight-chain C₁₆-C₂₄Fatty acid sorbitan fatty acid esters, sucrose fatty acid esters, alkylphenol ethoxylates or mixtures thereof, such as sorbitan monooleate, sorbitan laurate, diglycerin stearate, diglycerin monooleate, polyglycerol succinate, sucrose stearate, etc., the secondary emulsifier can provide the function of assisting emulsification and stabilizing the emulsion in conjunction with the primary emulsifier.

In step (1), the aqueous phase contains 1-10 wt% of water-soluble electrolyte, such as but not limited to 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9 wt% of water-soluble electrolyte, and the electrolyte is inorganic water-soluble salt selected from calcium chloride, magnesium sulfate, and calcium sulfate. The water-soluble electrolyte can minimize the solubility of the monomer and the cross-linking agent in water, and the size and the number of pores in the foam can be controlled by adjusting the adding amount of the electrolyte.

In step (1), the aqueous phase further comprises not more than 6% by weight of water-soluble sulfonate or sulfate containing allyl or acrylamide groups, including but not limited to 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6% by weight of water-soluble sulfonate or sulfate containing allyl or acrylamide groups, more preferably less than 4% by weight of total monomers; the water-soluble sulfonate or sulfate containing allyl or acrylamide groups is selected from any one of sodium p-styrenesulfonate, 3-allyloxy-2-hydroxy-1-propanesulfonic acid sodium salt, 2-acrylamide-2-methylpropanesulfonic acid, ethylene glycol monoallyl ether and the like.

In the step (1), the aqueous phase contains 1% to 15% of water-soluble initiator based on the total weight of the monomers, for example, including but not limited to 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15% of water-soluble initiator based on the total weight of the monomers, and the initiator is selected from persulfates, such as ammonium persulfate, sodium persulfate, potassium persulfate, and the like.

In the step (2), the emulsified high internal phase emulsion prepared in the step (1) is placed into a reaction container made of polymethyl methacrylate or polyethylene according to a certain thickness, the curing time is 8 hours to 24 hours in an oven or a water bath or UV irradiation, preferably, the curing temperature is 55 ℃ to 90 ℃, and after the curing is finished, the monomer conversion rate (calculated according to the mass percentage of the unreacted residual monomer in the total monomer) in the oil phase is not lower than 85%.

Wherein, in the step (3), the solidified foam is washed by deionized water and then is extruded and dehydrated by a compression roller, the washing and extrusion and dehydration processes can be repeated for several times, such as 1 time, 2 times, 3 times, 4 times, 5 times or more than 5 times, and the water content of the foam after extrusion and dehydration is not higher than 50% of the weight of the wet foam material before drying.

In step (3), the dehydrated foam is pressed through one or more washing processes, preferably drying at 60 ℃ to 100 ℃ for 6 hours, and the dried foam has a water content of not higher than 5% by weight of the foamed polymer, such as but not limited to 5%, 4.5%, 4%, 3.5%, 3%, 2.5%, 2%, 1.5%, 1%, 0.5% by weight of the polymer, and the dried foam has a calcium chloride content of not higher than 0.1% by weight of the foamed polymer, such as but not limited to 0.1%, 0.09%, 0.08%, 0.07%, 0.06%, 0.05%, 0.04%, 0.03%, 0.02%, 0.01% by weight of the foamed polymer.

In the preparation method of the high internal phase emulsion foam for the sanitary product, disclosed by the invention, a functional group in a reactive nonionic emulsifier structure in an oil phase can be polymerized with a monomer, so that a polar group in an emulsifier molecule is grafted in a cured foam polymer structure, and the foam has certain hydrophilicity which cannot be reduced along with the increase of the liquid adding times of the foam; meanwhile, compared with the traditional oil-soluble non-reactive emulsifier, the nonionic reactive emulsifier has less addition amount under the same shearing speed and mixing temperature, and the prepared emulsion is more stable and high-temperature resistant. The water-soluble reactive emulsifier (i.e. water-soluble allyl or acrylamide group-containing sulfonate or sulfate) in the water phase has similar action to the reactive emulsifier in the oil phase, and also has synergistic emulsification effect to make the emulsion more stable, but the addition amount thereof needs to be controlled within a certain range, preferably the content thereof is less than 2% by weight of the water phase, more preferably the content thereof is less than 1% by weight of the water phase, and the addition amount thereof is too high, which may cause the foam elasticity to be reduced and the absorption performance to be reduced.

The hydrophilicity of a foam can be characterized by the contact angle of the test liquid on the surface of the foam, the immersion time of the foam in the test liquid, the vertical wicking height of the foam, and the speed at which the foam absorbs the test liquid, and the multiple hydrophilicity is characterized by the contact angle of the foam to the test liquid after 5 test liquid treatments.

According to the invention, the oil-soluble reactive nonionic surfactant is added into the oil phase, and the water-soluble reactive stabilizer in the water phase assists in emulsification and preparation of the stable high internal phase emulsion, so that the foam material obtained after the prepared high internal phase emulsion is cured can have excellent repeated hydrophilicity without hydrophilic treatment.

The invention is not specially explained except that the reactive emulsifier is self-made, and other raw materials can be purchased from the market.

The properties of the foams prepared in the present invention were tested and characterized using the methods described below:

A) test liquid

The test liquid used in all tests in the present invention was artificial blood (standard synthetic liquid) as the test liquid. The preparation and physical properties of the standard synthetic liquid can be referred to the description in appendix K in the national standard G/T22875-2018. The test liquid was maintained at a temperature of (23. + -.1). degree.C. for all tests, a small amount of food coloring was added to the test liquid for easy visual identification during the test.

B) Preparation of foam samples

The cured foam sample was cut into a rectangle of 4 cm х 4 cm long by 4 mm wide and about 4 mm thick, and the foam sample was cut with a reciprocating saw, taking care to avoid the portion of the foam surface with particularly large holes or cracks or irregularities, and to ensure that the size and surface morphology of each foam sample were substantially consistent. Foam thickness was measured using a sponge thickness gauge.

C) Determination of contact Angle

The contact angle of the standard synthetic fluid on the foam samples made in the examples was measured using a Dataphysics model OCA25 video optical contact angle tester.

i) The cut foam sample was placed on the operating table and a 1 ml disposable syringe was used to withdraw the standard synthetic fluid, ensuring that no air bubbles were present in the syringe during the withdrawal.

ii) adjusting the stage position and viewing window so that the needle and sample are clearly visible in the screen, the needle being centered in the screen, the distance between the foam and the needle being moderate, taking care that the needle does not touch the foam and is not too close.

iii) setting the volume of the injection liquid to be 3uL, injecting the injection liquid discontinuously, observing that the tapping is immediately carried out to shoot when the liquid drop of the flowing synthetic liquid just contacts the foam sample after the liquid is injected by the tapping, and then measuring the contact angle.

iv) measuring 5ml of synthetic liquid, adding the synthetic liquid to the test foam, repeating the liquid adding for 4 times after the synthetic liquid is completely absorbed, and testing the contact angle of the foam after 5 times of liquid adding by referring to the steps i) to iii) after the last liquid adding is completely absorbed.

D) Measurement of the permeation time

Preparing 200 ml of test liquid in a 250 ml beaker, dropping the cut foam sample freely into the beaker at a position of a certain height of about 25 cm, immediately timing when the foam sample and the test liquid start to contact, observing the absorption state of the foam in the liquid, stopping timing when the test liquid completely soaks the foam, and recording the soaking time.

E) Determination of the absorption Rate

Weighing and recording the foam sample to be tested, and then referring to D) the test method of the soaking time, taking out the sample with a clamp immediately after the foam sample is immersed in the liquid for 1 minute, taking care not to squeeze the sample, weighing the weight of the taken-out sample, and the difference in the weight of the test liquid absorbed per unit mass of the foam sample per unit time after the foam is immersed in the test liquid is the absorption rate of the sample in grams per gram per minute.

F) Determination of vertical wicking Rate

Cutting the foam sample into a long rectangle 20 cm long, 1.5 cm wide and 4 mm thick, fixing the foam on a scale marked with a scale supported by an iron stand, as shown in fig. 2; the foam sample was approximately 2-5 mm below the bottom end of the ruler; placing a vessel containing dyed test liquid below the scale, when the test is started, lowering the scale until the liquid level is tangent to the scale 0 position of the scale, and immediately starting timing; the time to reach the 2cm position of the test liquid was recorded.

G) Determination of Water content and hydratable salt content

The water content is determined by weighing a mass of dried foam sample, placing the sample in an oven at 150 ℃, drying for 3 hours, weighing and calculating the weight difference of the foam sample before and after placing in the oven, i.e. the water content of the foam.

The content of the hydratable salt is determined by qualitative/quantitative analysis of an ICP inductively coupled plasma emission spectrometer, and then converted into the content of the hydratable salt.

The following embodiments are further described in the present invention, but not intended to limit the invention.

Example 1

A) Preparation of oil-soluble reactive nonionic emulsifier

Adding thionyl chloride into a four-neck flask with a stirring pipe, a reflux pipe, a dropping funnel and a thermometer at room temperature, starting stirring, dropwise adding acrylic acid, and completing dropwise adding within 1 hour; the temperature was then raised to 40 ℃ and HCl and SO were removed under reduced pressure₂Then pentaerythritol monostearate is added, HCl is removed to complete the reaction, and the obtained product is washed by brine and pure water and finally washed and desolvated by using an organic solvent to obtain the high-purity Acryloyl Pentaerythritol Monostearate (APMS).

B) Preparation of high internal phase emulsions

Calcium chloride (40.0 g), Sipomer COPS-1 (sodium allyl ether hydroxypropyl sulfonate, available from rolis, 1.2 g) was dissolved in 1000 ml of deionized water to make an aqueous phase; isooctyl acrylate (12.0 g), styrene (2.0 g), ethylene glycol dimethacrylate (6.0 g) were mixed with the self-prepared emulsifier acryloyl pentaerythritol monostearate (APMS, 3.0 g), Span 80(1.5 g) to make an oil phase which was slightly heated to 40 ℃ to facilitate dissolution of the emulsifier in the monomer. An initiator phase was prepared by weighing 2.5 grams of sodium persulfate to dissolve in 50 grams of deionized water.

Placing the obtained oil phase into a polypropylene container with the volume of 3 liters, stirring the oil phase by using an IKA stirrer, wherein the stirring paddle is an anchor type stirring paddle made of polytetrafluoroethylene, the total length of the paddle is about 8 cm, initially stirring the oil phase at the rotating speed of 500 revolutions per minute, simultaneously adding all the water phase within 5 minutes, preheating the water phase to 40 ℃ in advance, gradually increasing the stirring speed along with the addition of the water phase, rotating the speed at about 2000 revolutions per minute after all the water phase is added, adding an initiator solution after forming a stable and non-layered high internal phase emulsion, and then stirring for 5-10 minutes.

C) Curing of high internal phase emulsions

Pouring the prepared high internal phase emulsion into a curing mold made of polypropylene, wherein the mold is 24 cm long, 10 cm wide and 6 cm high, putting the mold filled with the emulsion into an oven at 90 ℃, and taking out after reacting for about 8 hours.

D) Washing, dewatering and drying of foam

Taking out the solidified foam, directly washing the foam by using normal-temperature deionized water to remove residual emulsifier and inorganic salt, then carrying out extrusion dehydration by using a stainless steel compression roller weighing about 2.0 kg, and repeating the washing and extrusion dehydration processes for several times according to actual conditions. And (3) putting the dehydrated foam into an oven at 60 ℃ for drying for 6 hours, and then taking out. The foam now has a water content of less than 5% (based on the weight of the dry foam) and a hydratable salt content of less than 0.1% (based on the weight of the dry foam).

Example 2

A) Preparation of oil-soluble reactive nonionic emulsifier

Weighing a certain amount of lithium chloride and Span 80, adding benzene as a solvent, stirring until the benzene is dissolved, and adding a certain amount of triethylamine to prepare a solution; adding acryloyl chloride into a four-neck flask with a stirring pipe, a reflux pipe, a dropping funnel and a thermometer at room temperature, dropwise adding the mixed solution while stirring at a low temperature of 0-5 ℃, and completing dropwise adding within 1 hour; after the addition, the temperature was raised to 40 ℃ for 4 hours. Removing HCl, washing the obtained product with 1% sodium bicarbonate aqueous solution, drying the obtained oil phase with magnesium sulfate overnight, and distilling off the solvent under reduced pressure to obtain high-purity acryloyl sorbitan oleate (ASMO).

B) Preparation of high internal phase emulsions

Dissolving calcium chloride (40.0 g), AMPS (2-acrylamido-2-methylpropanesulfonic acid sodium salt, available from Rodiya, 0.4 g) in 1000 ml of deionized water to obtain an aqueous phase; an oil phase was prepared by mixing lauryl acrylate (10.0 g), styrene (2.0 g), ethylene glycol dimethacrylate (8.0 g) with the self-prepared emulsifier acryloyl sorbitan oleate (ASMO, 1.0 g), Span 80(1.5 g) and slight heating of the oil phase to facilitate dissolution of the emulsifier in the monomer. 2.5 grams of potassium persulfate was weighed into 50 grams of deionized water and dissolved to produce an initiator phase.

Placing the obtained oil phase into a polypropylene container with the volume of 3 liters, stirring the oil phase by using an IKA stirrer, wherein the stirring paddle is an anchor type stirring paddle made of polytetrafluoroethylene, the total length of the paddle is about 8 cm, initially stirring the oil phase at the rotating speed of 500 revolutions per minute, simultaneously adding all the water phase within 5 minutes, preheating the water phase to 70 ℃ in advance, gradually increasing the stirring speed along with the addition of the water phase, rotating the speed at about 1000 revolutions per minute after the addition of all the water phase, adding an initiator solution after forming a stable and non-layered high internal phase emulsion, and then stirring for 5-10 minutes.

C) Curing of high internal phase emulsions

Pouring the prepared high internal phase emulsion into a curing mold made of polypropylene, wherein the mold is 24 cm in length, 10 cm in width and 6 cm in height, putting the mold filled with the emulsion into an oven at 70 ℃, reacting for about 14 hours, and taking out.

The subsequent post-treatment process conditions were all identical to those in example 1.

Example 3

Dissolving sodium chloride (20.0 g) and SSS (sodium p-styrene sulfonate, alatin, 1.2 g) into 1800 ml of deionized water to prepare a water phase; an oil phase was prepared by mixing octadecyl acrylate (15.0 g), alpha-ethylstyrene (3.0 g), 1, 6-hexanediol dimethacrylate (2.0 g) with the self-prepared emulsifier acryloyl pentaerythritol monostearate (APMS, 7.6 g), sucrose fatty acid ester S-370 (available from Mitsubishi chemical, 0.9 g). An initiator phase was prepared by weighing 3.0 grams of ammonium persulfate to dissolve in 50 grams of deionized water.

The subsequent curing process and post-treatment process conditions were exactly the same as in example 1.

Example 4

Calcium sulfate (85.0 g) was dissolved in 1000 ml of deionized water to prepare an aqueous phase; the oil phase was prepared by mixing isooctyl methacrylate (31.5 g), divinylbenzene (55% purity, from alatin, 13.5 g) with the self-prepared emulsifier acryloyl pentaerythritol monostearate (APMS, 2.0 g), citrrol DPHS (PEG-30 dipolyhydroxystearate, from CRODA, 3.0 g). An initiator phase was prepared by weighing 0.5 grams of sodium persulfate dissolved in 50 grams of deionized water.

Placing the obtained oil phase into a polypropylene container with the volume of 3 liters, stirring the oil phase by using an IKA stirrer, wherein the stirring paddle is an anchor type stirring paddle made of polytetrafluoroethylene, the total length of the paddle is about 8 cm, initially stirring the oil phase at the rotating speed of 500 revolutions per minute, simultaneously adding all the water phase within 5 minutes, preheating the water phase to 40 ℃ in advance, gradually increasing the stirring speed along with the addition of the water phase, rotating the speed at about 3000 revolutions per minute after all the water phase is added, adding an initiator solution after forming a stable and non-layered high internal phase emulsion, and then stirring for 5-10 minutes.

Comparative example 1

Span 80 in example 1 was replaced with an equal mass of APMS, so that the emulsifier in the oil phase was 4.5 grams of APMS, the remaining components were unchanged, and the emulsification process and subsequent solidification and washing, dewatering and drying processes were identical to those described in example 1.

Comparative example 2

The Acrylated Pentaerythritol Monostearate (APMS) in example 1 was replaced with an equal mass of Span 80, so that the emulsifier in the oil phase was 4.5 g of Span 80, the remaining components were unchanged, the emulsification process and the subsequent solidification and washing, dehydration and drying processes were in accordance with the method described in example 1.

Comparative example 3

And (3) adding no Sipomer COPS-1 into the water phase in the comparative example 2, keeping the other components consistent, solidifying, soaking the washed and dehydrated foam in a2 mass percent Span 20 aqueous solution for saturation, then extruding and dehydrating by using a compression roller, repeating the saturation of the Span 20 aqueous solution and the extrusion by using the compression roller, repeating the process for 3 times, and finally drying the treated foam, wherein the drying condition is consistent with the method described in the example 1.

Comparative example 4

The aqueous phase from comparative example 2 was not subjected to the Sipomer COPS-1 addition, the remaining components were unchanged, and the subsequent curing and washing, dewatering and drying procedures were in accordance with the method described in example 1.

Comparative example 5

The amount of Sipomer COPS-1 added to the aqueous phase in example 1 was increased to 5 grams, the remaining components were unchanged, the emulsification process and the subsequent solidification and washing, dewatering and drying processes were identical to those described in example 1.

All foam samples prepared in the examples and comparative examples were tested for contact angle, soak time, vertical wicking speed, and absorption time using the test methods described above. The test results are shown in Table 1.

TABLE 1 foam sample Performance test data prepared in examples and comparative examples

As can be seen from the test results in table 1, when APMS/COPS-1 is used as the emulsifier (example 1), the hydrophilicity of the foam sample is significantly improved, the vertical wicking speed and the penetration time are equivalent to those of the high internal phase emulsion foam prepared by the conventional emulsifier after hydrophilization treatment (comparative example 3), but the results of the multiple hydrophilic example 1 are better, as can be seen from the contact angle results of the foam and the test liquid in fig. 3 and 4, the contact angle of the foam sample (left panel) in example 1 after 5 times of liquid filling has no significant change compared with the first contact angle test result, while the contact angle of the foam sample (right panel) in comparative example 3 after 5 times of liquid filling has a rising trend, which indicates that the hydrophilic substance is lost and the hydrophilicity is reduced with the increase of the liquid filling times. In comparative example 1, only APMS is used as a main emulsifier, experiments show that the emulsifying effect is not as good as that of the compound with Span 80, the diameter of the emulsified liquid drop is larger, the pore diameter of the dry foam is larger, and compared with the number average pore diameter of 60-80 μm (shown in figure 1) in example 1, the number average pore diameter of comparative example 1 reaches 90-120 μm, which is probably because the HLB value of APMS is higher, and the liquid drop can be more stably existed in the system by being compounded with Span 80 with lower HLB value; in addition, in comparative example 5, although the hydrophilicity of the foam prepared was improved, the addition amount of the stabilizer COPS-1 was controlled within a certain range since the addition amount of COPS-1 was too high, which resulted in a sharp increase in cell diameter and a decrease in specific foam surface area, which directly affected the deterioration of wicking absorption properties and a decrease in foam elasticity. In example 4, no allyl or acrylamide sulfonate or sulfate was added to the aqueous phase, which decreased the hydrophilicity of the foam and decreased the emulsion stability as compared to example 1, it can be seen that COPS-1 or SSS in the aqueous phase not only increased the hydrophilicity of the foam, but also was beneficial to the emulsion stability during emulsification.

While the present invention has been described in detail with reference to the preferred embodiments, it should be understood that the above description should not be taken as limiting the invention. It will be appreciated by those skilled in the art that modifications or adaptations to the invention may be made in light of the teachings of the present specification. Such modifications or adaptations are intended to be within the scope of the present invention as defined in the claims.

Claims

1. A method for preparing a high internal phase emulsion foam without hydrophilic post-treatment comprising the steps of:

1) preparing a water-in-oil emulsion comprising an oil phase, wherein the oil phase comprises, by weight of the oil phase:

the oil-soluble emulsifier in b) of the oil phase comprises:

i) at least 40 wt% of the emulsifier component of an oil-soluble polymerizable first emulsifier, wherein the polymerizable first emulsifier is an unsaturated fatty acid ester emulsifier containing a plurality of hydroxyl groups; ii) at least 10% by weight of the emulsifier component of an oil-soluble non-reactive second emulsifier, said emulsifier being soluble in the oil phase and capable of forming a stable water-in-oil emulsion; the first emulsifier is selected from an acryloyl polyol fatty acid ester;

the water phase of the water-in-oil emulsion comprising: a) 1-10 wt% of water-soluble electrolyte based on the weight of the aqueous phase, wherein the electrolyte is inorganic water-soluble salt; b) 0-6% by weight of water-soluble sulfonate or sulfate salts containing allyl or acrylamide groups, based on the total weight of the monomers in the oil phase, and less than 2% by weight of the aqueous phase; c) a water-soluble initiator accounting for 1-15% of the total weight of the monomers in the oil phase;

2) curing the water-in-oil emulsion to form a foam; curing in a manner of putting into an oven, water bath or UV light irradiation;

2. The method of preparation according to claim 1, wherein the water phase of the water-in-oil emulsion is:

a) the inorganic water-soluble salt is selected from monovalent or divalent inorganic salts of alkali metal and halide or sulfate of alkali metal;

b) the water-soluble sulfonate or sulfate containing allyl or acrylamide is selected from at least one of sodium allyl ether hydroxypropyl sulfonate, sodium 2-acrylamido-2-methyl propane sulfonate and sodium p-styrene sulfonate;

c) the water-soluble initiator is selected from persulfates.

3. The production method according to claim 2, wherein the water-soluble initiator is selected from any one of potassium persulfate, sodium persulfate, or ammonium persulfate.

4. The method according to any one of claims 1 to 3, wherein the weight ratio of the volume of the water phase to the oil phase of the water-in-oil emulsion is 10mL to 80 mL: 1 g.

5. The method according to claim 4, wherein the monomer component in a) of the oil phase comprises:

i) from 60 to 95 weight percent of at least one substantially water-insoluble monofunctional comonomer, based on the total weight of monomers contained in the oil phase;

ii) 5 to 40 weight percent of at least one substantially water-insoluble multifunctional crosslinker, based on the total weight of monomers contained in the oil phase.

6. The method according to claim 5, wherein, in the monomer component in a) of the oil phase:

i) the monofunctional comonomer is selected from the group consisting of styrene, alkyl acrylate, alkyl methacrylate, and mixtures thereof;

ii) the multifunctional crosslinking agent is selected from divinyl aromatics, alkyl acrylamides, diacrylates or dimethacrylates of polyols and mixtures thereof.

7. The method according to claim 6, wherein the monomer component in a) of the oil phase comprises:

i) from 70% to 90% by weight of a monofunctional comonomer component selected from: acrylic acid C₄-C₁₈Alkyl esters, methacrylic acid C₄-C₁₈Alkyl esters, styrene, and mixtures thereof;

ii) 10 to 30 weight percent of a multifunctional crosslinking agent selected from the group consisting of divinylbenzene, divinyltoluene, divinylxylene, ethylene glycol dimethacrylate, 1, 6-hexanediol dimethacrylate, and mixtures thereof.

8. The method according to claim 4, wherein the oil-soluble emulsifier in b) of the oil phase comprises:

i) an oil-soluble polymerizable first emulsifier comprising not less than 50% by weight of the emulsifier component, the first emulsifier being selected from the group consisting of acryloyl sorbitan stearate, acryloyl sorbitan oleate, acryloyl pentaerythritol monostearate, acryloyl pentaerythritol monooleate, or acryloyl sucrose fatty acid monoester, and mixtures thereof; ii) an oil-soluble non-reactive second emulsifier which accounts for not less than 20 percent of the weight of the emulsifier component, wherein the second emulsifier is selected from glycerin fatty acid ester, polyglycerol fatty acid ester, sorbitan fatty acid ester, sucrose fatty acid ester or alkylphenol ethoxylate and a mixture thereof.

9. The preparation method of claim 1, wherein the temperature for mixing and emulsifying the oil phase and the water phase in the step 1) is 40-80 ℃, and the stable water-in-oil emulsion is formed at a mixing and shearing speed of 500-3000 rpm.

10. The preparation method of claim 9, wherein the emulsified high internal phase emulsion prepared in step 1) can be stably placed at a temperature of 40-80 ℃ for more than 2 hours, and a phenomenon of separation of anhydrous oil occurs.

11. The preparation method of claim 1, wherein the curing temperature of the water-in-oil emulsion in the step 2) is 55 ℃ to 150 ℃, and the curing time is not less than 8 hours.

12. The method of claim 1, wherein the high internal phase emulsion foam produced in step 3) without a hydrophilic post-treatment has a final water content of less than 5% and a hydratable salt content of less than 0.1%.

13. A high internal phase emulsion foam prepared by the process of any one of claims 1 to 12 without hydrophilic post-treatment.

14. The high internal phase emulsion foam material without hydrophilic post-treatment according to claim 13, characterized in that the foam material has a foam number average cell diameter of 30 to 100 μm and a fenestration number average diameter between adjacent bubbles is below 20 μm.

15. A high internal phase emulsion foam without hydrophilic post-treatment according to claim 13 or 14 characterized in that the foam has a vertical wicking speed at 2cm absorption height of less than 13min, a soaking time of less than 40s and an absorption speed of more than 20 g/g/min.

16. The high internal phase emulsion foam without hydrophilic post-treatment of claim 15 wherein the foam has a contact angle with the test liquid of less than 60 ° and no increase in contact angle with multiple injections of the test liquid and is more hydrophilic than the test liquid.

17. Use of a high internal phase emulsion foam prepared by the preparation method of any one of claims 1 to 12 without hydrophilic post-treatment or a high internal phase emulsion foam prepared by the preparation method of any one of claims 13 to 16 without hydrophilic post-treatment for the preparation of hygienic absorbent articles.

18. Use of a high internal phase emulsion foam material without hydrophilic post-treatment for the manufacture of sanitary absorbent articles according to claim 17, characterized in that it is used in baby diapers, adult incontinence products, medical bandages or feminine napkins.