CN106633987A - Method for strengthening light fiber composite material - Google Patents

Abstract

A strengthening method and application of a light-weight fiber composite material, the method is as follows: take plant fiber scraps and perform pretreatment to obtain plant fiber raw materials; form blanks through forming and heating and hardening, wherein, when forming blanks, sizing The final mixed fiber is quantitatively and evenly paved in the forming frame; or the mixture of plant fiber and synthetic fiber is formed by air-laid needle punching; and then the blank is impregnated with a foamable agent, high-temperature setting and surface reprocessing. into a flat plate or a special-shaped composite material; wherein, the impregnated foamable preparation is quantitatively formulated according to product design requirements, and the foamable preparation is penetrated into the interior of the blank during impregnation; the foamable preparation at least includes a foamable Foam phenolic resin, foaming agent and surfactant, and one or more of curing agent, modifier and flame retardant can also be added. It can be used to make high-strength artificial lightweight composite boards, and the prepared fiber composite boards have low density and good mechanical properties.

Description

A method for strengthening lightweight fiber composite materials

technical field

The invention relates to the technical field of novel wood-based panels, in particular to a method for strengthening lightweight fiber composite materials.

Background technique

Further weight reduction under the premise of ensuring the physical and mechanical properties of composite materials is one of the important needs of the industry for material performance and cost. Especially in passenger transport industries such as automobiles and high-speed rail, light weight, comfort and environmental protection are the main trends in development. At present, GMT (glass mat reinforced thermoplastics) materials made of glass fiber and synthetic fiber mat are most commonly used in the automotive interior industry. With the enhancement of environmental protection awareness and cost considerations, in recent years, natural plant fibers have been used to replace glass fibers. A large number of documents and patents at home and abroad have reported the research and application of hemp fiber reinforced composite materials. The ratio of hemp fiber to synthetic fiber is about (40-65): (35-60), and according to different application requirements, it is To meet certain mechanical properties, the density of composite products generally exceeds 0.8g/cm ³ , and products with a density lower than 0.5g/cm ³ are usually only used as decorative materials. Other natural and environmentally friendly plant fibers with high aspect ratios, such as wood fibers, bamboo fibers, cotton fibers, and crop straw fibers, have not been widely used in the preparation of non-woven felts.

At the same time, the physical and mechanical properties of wood-based fiberboards commonly used in furniture and decoration are closely related to their density. When the product density is lower than 0.4g/ ^cm3 , its performance can only meet the decorative performance requirements.

Foaming is an important means to reduce the density of materials. There has been a long history of research on the preparation of lightweight materials by polymer foaming. For example, most of the base materials for headliners produced by domestic automotive interior manufacturers are phenolic resin felt, EVA (ethylene-vinyl acetate copolymer) and polyurethane. Foam materials, polyurethane foam materials, etc. Although these materials have excellent characteristics such as sound absorption, heat insulation and shock absorption, they usually cannot withstand large external forces. Reducing the density while meeting the strength requirements is an important technical problem that the wood-based panel industry and even the composite material industry need to break through.

Contents of the invention

The main purpose of the present invention is to provide a method for strengthening lightweight fiber composite materials. The fiber composite materials prepared by the method have lower density and good mechanical properties.

To achieve the above object, the present invention takes the following design scheme:

A method for strengthening a lightweight fiber composite material, the method steps are as follows:

1) taking plant fiber scraps, and performing pretreatment to obtain plant fiber raw materials;

2) The blank is formed by forming a blank and heating and hardening, wherein, when forming a blank, the mixed fiber after sizing is quantitatively and uniformly paved in the forming frame; or the mixture of plant fiber and synthetic fiber is formed by air-flow paving and needle punching;

3) The blank is then subjected to the process of impregnating the foamable preparation, high temperature setting and surface reprocessing to make a flat plate or special-shaped composite material; wherein, the impregnated foamable preparation is quantitatively prepared according to product design requirements and can Foaming preparation, the foaming preparation penetrates into the interior of the billet during impregnation; the foamable preparation includes at least a foamable phenolic resin, a foaming agent and a surfactant, and a curing agent, a modifier and a flame retardant can also be added one or more of.

In the strengthening method of the lightweight fiber composite material, the addition ratio of the foamable phenolic resin, foaming agent, surfactant, curing agent, modifier and flame retardant is 100:(1～10) :(1～5):(0～3):(0～20):(0～15).

In the strengthening method of the lightweight fiber composite material, the foaming agent is n-pentane, normal hexane and/or foaming agent H; the surfactant is Tween-80, dodecylbenzene sodium sulfonate and/or siloxane; the curing agent is p-toluenesulfonic acid, xylenesulfonic acid and/or oxalic acid; the modifier is isocyanate, polyvinyl acetate, polyvinyl alcohol and/or polyvinyl alcohol Ethylene glycol; the flame retardant is an organic or inorganic phosphorus nitrogen flame retardant.

In step 2) of the strengthening method of the lightweight fiber composite material, an adhesive is applied to the plant fiber raw material during the stirring process, specifically: a phenolic adhesive or a melamine-modified urea-formaldehyde adhesive is evenly sprayed on the surface of the plant fiber during the stirring process , Polyvinyl acetate or polyvinyl alcohol liquid adhesive, the application amount is 8-20%.

In the step 2) of the strengthening method of the lightweight fiber composite material, polypropylene fiber, polyethylene fiber or polylactic acid fiber is mixed with the plant fiber raw material, and the mixing ratio is (70-90):(10-30).

In the reinforcement method of the lightweight fiber composite material, it also has at least one of the following features:

①The heating and hardening process in step 2) of the method is to control the loose fiber blanks after paving by using gauges, clamps or pressing plates until reaching a preform with a density of 0.1 to 0.3g/cm ³ , Then send it to the oven or hot press heating equipment for further processing, the heating temperature is 80-170°C, and the heating time is 1-5min/mm;

②The high-temperature shaping process in step 3) of the method is: pave the impregnated blank quantitatively in a flat-pressed backing plate or a special-shaped mold, apply a pressure of 0.3-1.0 MPa on the mold, and press the slab to a density of 0.15-0.65 g/cm ³ semi-finished products; wherein, the high temperature is 80-180°C, and the setting time is 1-10min/mm.

In the strengthening method of the lightweight fiber composite material, the plant fiber is at least one of hemp, wood, bamboo, cotton stalk and straw fiber; the scraps of the plant fiber are prepared after pretreatment and have a length of 5-5 50mm, diameter of 0.05 ~ 2mm, moisture content of 2 ~ 6% fiber bundle form.

In step 3) of the strengthening method of the lightweight fiber composite material, when the blank is impregnated, the upper and lower surfaces of the blank are immersed in a certain amount of adhesive solution under normal pressure or by decompression and pressure. The pressure method makes the glue evenly dispersed.

In the strengthening method of the lightweight fiber composite material, the surface reprocessing is to carry out surface treatment on the semi-finished product and then perform veneer processing, and the veneer material is veneer, impregnated paper, plastic film or textile cloth.

In the strengthening method of the lightweight fiber composite material, the pretreatment at least includes softening and rubbing treatment, or further drying and/or screening treatment.

The present invention will be described in further detail below in conjunction with specific embodiments.

Example 1

1) Weigh 90kg of bamboo fiber and 10kg of polyethylene fiber, and after the two materials are evenly mixed, they are opened, carded, cross-laid in the vertical and horizontal directions, and then felted by upper and lower needle punching to obtain a density of 0.12g/cm ³ and a bamboo fiber/polyethylene fiber composite felt with a thickness of 30mm; put the composite felt into a hot press at 140°C and press it into a blank with a thickness of 20mm for later use;

2) After mixing the phenolic adhesive, n-hexane, and Tween-80 at a high speed according to the ratio of 100:5:3 by mass, then add 5% polyisocyanate and stir evenly, and impregnate the billet into the adhesive solution with the same weight as the billet under normal pressure, and pass The extrusion method makes the glue evenly dispersed; the blank is put into a molding machine at a temperature of 140°C to 150°C for solidification and molding, and then cooled and cut after being taken out to prepare a lightweight composite board.

The lightweight fiber composite material obtained in this example has a final density of 0.35 g/cm ³ , a static bending strength of 16 MPa, an internal bond strength of 0.2 MPa, and a 24-hour absorption thickness expansion rate of <2%.

Example 2

1) Weigh 90kg wood fiber and 10kg EVA emulsion, add quantitative water to the EVA emulsion to reduce the viscosity, spray evenly on the surface of wood fiber in the glue mixer, and then use paving equipment to evenly pave in the forming frame, pre-press to A soft billet with a density of 0.15g/ ^cm3 and a thickness of 30mm; dry the billet in an oven at 100°C for 2 hours and take it out for use;

2) After the phenolic adhesive, n-hexane, and Tween-80 are mixed at high speed according to the mass ratio of 100:6:5, then add 5% water-based isocyanate and stir evenly, and the upper and lower surfaces of the billet are immersed in the adhesive solution of equal weight under normal pressure. The glue is uniformly dispersed by extrusion; the blank is put into a hot press at a temperature of 120°C to 130°C for hot pressing and solidification, and after being taken out, it is cooled and cut to prepare a lightweight composite board.

The composite material obtained in this example has a final density of 0.40 g/cm ³ , a static bending strength of 20 MPa, an internal bonding strength of 0.5 MPa, and a 24-hour absorption thickness expansion rate of <3%.

Example 3

Weigh the raw material (kg) according to the following weight:

1) Take by weighing 90kg of flame-retardant wood fiber, 10kg of melamine-modified urea-formaldehyde resin adhesive, spray the adhesive on the surface of the wood fiber, and lay it on the surface, and the density of the blank is 0.20g/ ^cm3 in a hot press at 120°C;

2) After mixing the phenolic adhesive, n-pentane and sodium dodecylbenzenesulfonate at a high speed in a mass ratio of 100:4:3, add 5% water-based isocyanate and 6% trimethylolphosphine oxide and stir evenly, divide the billets into The upper and lower surfaces are pressurized and dipped into an adhesive solution of equal weight; the preform is put into a hot press at a temperature of 130°C to 150°C for hot pressing and curing molding.

The composite material obtained in this example has a final density of 0.34g/cm ³ , a static bending strength of 18MPa, an internal bonding strength of 0.25MPa, a 24-hour absorption thickness expansion rate of <6%, and an oxygen index of 32%.

Example 4

1) Weigh 80kg of wood fiber and 20kg of polypropylene fiber, mix the two materials evenly, open, card, cross-lay in the vertical and horizontal directions, and then go through the upper and lower needles to form a felt to obtain a density of 0.15g/cm ^3. A wood fiber/polypropylene fiber composite felt with a thickness of 20mm; put the composite felt into a 170°C hot press and press it into a blank with a thickness of 15mm for later use;

3) After mixing the phenolic adhesive, n-hexane, and Tween-80 at a high speed according to the ratio of 100:8:2 by mass, then add 2% polyisocyanate and stir evenly, and impregnate the billet into the adhesive solution with the same weight as the billet under reduced pressure. The extrusion method makes the glue evenly dispersed; the blank is put into a molding machine at a temperature of 140°C to 150°C for solidification and molding, and then cooled and cut after being taken out to prepare a lightweight composite board.

The lightweight fiber composite material obtained in this example has a final density of 0.40 g/cm ³ , a static bending strength of 18 MPa, an internal bond strength of 0.3 MPa, and a 24-hour absorption thickness expansion rate of <2%.

Example 5

1) Take by weighing 90kg reclaimed hemp fiber and 10kg polypropylene fiber, after the two materials are evenly mixed, loosen, card, cross-lap in the vertical and horizontal directions, and then be felted by upper and lower needle punching to obtain a density of 0.12g/ Hemp fiber/polypropylene fiber composite felt with a thickness of ³ cm and a thickness of 40 mm; put the composite felt into a hot press at 170 ° C and press it into a blank with a thickness of 35 mm for later use;

3) After mixing the phenolic adhesive, n-pentane and sodium dodecylbenzenesulfonate at a high speed in a mass ratio of 100:4:2, add 4% water-based isocyanate and 6% trimethylol phosphine oxide and stir evenly, divide the blank into The upper and lower surfaces are pressurized and dipped into 1.5 times the weight of the adhesive solution; the assembly is put into a hot press at a temperature of 130°C to 150°C for hot pressing and curing.

The lightweight fiber composite material obtained in this example has a final density of 0.41 g/cm ³ , a 24-hour absorption thickness expansion rate of <2%, a 24-hour water absorption rate of <2%, and a static bending strength of >10 MPa.

Example 6

1) Weigh 92kg of bamboo fiber and 8kg of PVA (polyvinyl alcohol) solution, spray the PVA solution evenly on the surface of the wood fiber in the glue mixer, and then use the paving equipment to evenly pave in the forming frame, pre-pressed to a density of 0.15 g/cm ³ A soft billet with a thickness of 40mm; dry the billet in an oven at 110°C for 3 hours and take it out for use;

2) After the phenolic adhesive, n-hexane and sodium dodecylbenzenesulfonate are mixed at high speed according to the ratio of 100:5:5 by mass, then add 6% water-based isocyanate and stir evenly. In the adhesive solution, the glue solution is uniformly dispersed by plane extrusion; the blank is placed in a hot press at a temperature of 130°C to 140°C for hot pressing and solidification molding, and then cooled and cut after being taken out to prepare a lightweight composite board.

The final density of the composite material obtained in this example is 0.30g/cm ³ , the static bending strength is >12MPa, the internal bond strength is >0.2MPa, and the 24-hour absorption thickness expansion rate is <3%.

The above-mentioned embodiments can be changed without departing from the scope of the present invention, so the above descriptions should be regarded as illustrative rather than limiting the protection scope of the patent application of the present invention.

Claims (9)

1. a kind of intensifying method of light fibre composite, it is characterised in that the method step is as follows：

1) string particle is taken, and is pre-processed, obtain plant fiber material；

2) blank is made in Jing assemblies and heat hardening, wherein, during assembly, the composite fibre after applying glue is carried out calmly in shaping frame Amount is uniformly mated formation；Or string and synthetic fibers mixing are molded using airflow pavement acupuncture；

3) again blank carried out into the process treatment process of impregnation of expandable preparation, high-temperature shaping and re-surface, makes flat board Or special-shaped composite；Wherein, described impregnation of expandable preparation is quantitatively to allot expandable preparation according to product design requirement, Effervescent preparations are made to infiltrate through inside blank during dipping；The expandable preparation at least include expandable phenolic resin, foaming agent and Surfactant, can also add one or more in curing agent, modifying agent and fire retardant.

2. the intensifying method of light fibre composite according to claim 1, it is characterised in that：Described expandable phenol The adding proportion of urea formaldehyde, foaming agent, surfactant, curing agent, modifying agent and fire retardant is 100:(1～10):(1～5): (0～3):(0～20):(0～15).

3. the intensifying method of light fibre composite according to claim 2, it is characterised in that：Described foaming agent is Pentane, n-hexane and/or blowing agent H；Described surfactant is Tween-80, neopelex and/or silica Alkane；Described curing agent is p-methyl benzenesulfonic acid, xylene monosulfonic acid and/or oxalic acid；Described modifying agent is isocyanates, poly-vinegar acid Vinyl acetate, polyvinyl alcohol and/or polyethylene glycol；Described fire retardant is organic or inorganic phosphorus-nitrogen containing flame retardant.

4. the intensifying method of light fibre composite according to claim 1, it is characterised in that methods described step 2) In, the plant fiber material applies adhesive in whipping process, specially：It is uniform to plant fibre surface in whipping process Spray plus modified phenolic adhesive, melamine modified urea-formaldehyde glue stick, polyvinyl acetate or polyvinyl alcohol liquid adhesive, applied amount 8～20%.

5. the intensifying method of light fibre composite according to claim 1, it is characterised in that methods described step 2) In, the plant fiber material applies adhesive in whipping process, specially：Mix poly- third in the plant fiber material Alkene fiber, polyethylene fibre or acid fiber by polylactic, mixed proportion is (70～90):(10～30).

6. the intensifying method of light fibre composite according to claim 1, it is characterised in that also at least have as follows One of feature：

1. methods described step 2) in heat hardening process, be by the loose blank of the fiber after mating formation, using thickness-determining gauge, fixture Or pressing plate is controlling loose blank until reaching density for 0.1～0.3g/cm³Prefabrication, be re-fed into baking oven or hot press add Further process in hot equipment, heating-up temperature is 80～170 DEG C, the heat time is 1～5min/mm；

2. methods described step 3) in high-temperature shaping process be：Impregnated stock is quantitatively mated formation in concora crush backing plate or xenotype mold It is interior, the pressure of 0.3～1.0MPa is applied on mould, slab is pressed into into 0.15～0.65g/cm of density³Semi-finished product；Its In, described high-temperature temperature is 80～180 DEG C, and shaping time is 1～10min/mm；

3. described string is at least the one kind in fiber crops, timber, bamboo wood, cotton stalk and stalk fibre；The particle of string The fibre bundle form that length is 5～50mm, a diameter of 0.05～2mm, moisture content is 2～6% is prepared into after pretreatment.

7. the intensifying method of light fibre composite according to claim 1, it is characterised in that methods described step 3) In, when blank impregnates, by the blank at ambient pressure or by decompression and pressuring method, point upper and lower surface impregnation is to quantitative glue In stick solution, make glue dispersed by fashion of extrusion.

8. the intensifying method of light fibre composite according to claim 1, it is characterised in that：Described surface adds again Work be semi-finished product are surface-treated after carry out veneer processing, surface lining is veneer, dipping paper, plastic foil or weaving cloth Material.

9. the intensifying method of light fibre composite according to claim 1, it is characterised in that：Described pretreatment is extremely It is few to include that softening and rub with the hands mill is processed, or further dried and/or screening process.