JP6948633B2 - Manufacturing method of composite molded material using bagasse fiber - Google Patents

Description

The present invention relates to a method for producing a composite molded material obtained by kneading bagasse fiber, which is a squeezed residue of sugar cane, and polypropylene.

In recent years, a plant fiber composite material obtained by kneading bagasse fiber, which is a squeezed residue of sugar cane, and polypropylene to prepare a composite pellet and then injection molding or heat pressing has been carried out.
Bagasse fiber has high strength and light weight, but can be obtained in large quantities at low cost. Polypropylene has the lowest specific gravity among versatile plastics, has excellent heat resistance and durability, and is also available at low cost. Therefore, the composite material made of bagasse fiber and polypropylene can be expected to be used in various fields as an inexpensive composite molding material.
However, polypropylene, which is crude water, and bagasse fiber, which is hydrophilic, are not well-adapted even if they are kneaded from the beginning.
Therefore, modified polypropylene graft-polymerized with maleic anhydride is kneaded into bagasse fiber and polypropylene to improve the adhesion between the fiber and the resin, and increase the rigidity, strength and impact value of the composite molded material made of the bagasse fiber and polypropylene. The method is known (Patent Document 1).

However, in order to knead dried bagus fibers, polypropylene, and modified polypropylene, heat treatment at a high temperature of around 200 ° C is required, and during kneading, the fibers come into contact with each other, and between the fibers and the polymer, and between the fibers and the metal surface. As a result of the frictional heat generated due to the friction between the fibers, the bagus fibers are locally further heated to cause thermal decomposition, which contaminates the mold by carbonizing or coloring the polymer, and also has an unpleasant odor. There was a problem such as issuing.
Therefore, the present inventor has found a method of reducing the contamination of the mold and increasing the heat resistant temperature of the composite molded material by 50 ° C. or more by removing the sugar remaining in the bagasse fiber with warm water.
However, even with this method, the sweet odor peculiar to sugar cane remains, and the surface becomes uneven due to moisture absorption in the air, which makes it impossible to reduce the deterioration of smoothness. Therefore, for example, automobile interior parts, etc. It has not yet been used in familiar products.

Japanese Patent No. 4370416 JP-A-2015-13916

The present invention has been made from the above viewpoint, and is a composite molding material formed by kneading bagasse fiber, which is a squeezed residue of sugar cane, and polypropylene. The surface is smooth and the sweet odor peculiar to sugar cane is removed. An object of the present invention is to provide a composite molded material.

In addition, Patent Document 2 discloses an invention that prevents the progress of coloring and the generation of offensive odor of a plant fiber reinforced thermoplastic resin material in which a resin material is compounded with a plant fiber, and reduces the tar-like component adhering to the mold surface. However, since the plant fiber in the present invention is the fiber of the residue of the palm palm fruit bunch after the fruit and oil are removed, the bagasse fiber, which is the object of the present invention, remains after squeezing. It differs in the chemical composition such as oil content or sugar content.
That is, the reduction of offensive odor, which is the object of the invention according to Patent Document 2, is intended for offensive odor generated due to "burning" in the manufacturing process of the plant fiber reinforced thermoplastic resin material. It is different from the sweet odor peculiar to sugar cane generated due to "residual sugar" like the target bagasse fiber.

The method for producing a composite molded material using bagasse fibers according to the present invention is as follows.
Bagasse fiber,
After acetylation (converting the hydroxyl groups of bagasse fibers into acetyl groups) by immersing them in acetic anhydride and heating them,
By kneading with polypropylene and injection molding or heat pressing the composite
It is characterized in that a composite molded material in which the sweet odor peculiar to sugar cane is significantly reduced while maintaining the smoothness of the surface can be obtained.

1) Compared with the conventional plant fiber composite material, the composite molded material according to the present invention suppresses water absorption, so that an increase in surface roughness (Rz) over time can be suppressed and deterioration of smoothness can be reduced. ..
2) The composite molded material according to the present invention is subjected to an alkali treatment before the acetylation treatment, so that deterioration of mechanical properties over time is suppressed as compared with the conventional plant fiber composite material, and further mechanical The nature can be improved.
3) Compared with the conventional bagasse fiber composite material, the composite molding material according to the present invention maintains the smoothness of the molding material surface without impairing its physical properties, and significantly reduces the sweet odor peculiar to sugarcane and stimulates it. Since the odor is also suppressed, it can be used for living spaces and products that people touch (for example, building materials and interior parts of automobiles).

A graph showing the weight increase rate of the composite molded material according to Example 1. Photograph of the composite molding material according to Example 1. Photograph of the composite molding material according to Example 1. A graph showing the surface roughness of the composite molded material according to Example 1. A graph showing the surface roughness of the composite molded material according to Example 1. A graph showing the measurement results of the surface roughness and the water absorption rate of the composite molded material according to Example 1 over time. A graph showing changes in the mechanical properties of the composite molded material according to Example 1. A graph showing the difference in mechanical properties of the composite molded material according to Example 1. Micrograph of the surface of the composite molding material Micrograph of the surface of the composite molding material Micrograph of the surface of the composite molding material Micrograph of the surface of the composite molding material Micrograph of the surface of the composite molding material Micrograph of the surface of the composite molding material Micrograph of the surface of the composite molding material Micrograph of the surface of the composite molding material Table showing the results of the odor sensory test Table showing the results of the odor sensory test A graph showing the moisture reduction rate of the composite molded material according to Example 2. A graph showing the weight increase rate of the composite molded material according to Example 2. A graph showing the weight increase rate of the composite molded material according to Example 2. A graph comparing changes in the mechanical properties of the composite molded material according to Example 2. Micrograph of the surface of the composite molding material Micrograph of the surface of the composite molding material Micrograph of the surface of the composite molding material Micrograph of the surface of the composite molding material Micrograph of the surface of the composite molding material Micrograph of the surface of the composite molding material Table showing the results of the odor sensory test Table showing the results of the odor sensory test Table showing the results of the odor sensory test Table showing the results of the odor sensory test Table showing the results of the odor sensory test

(Example 1)
1. 1. A method for producing a composite molded material using bagasse fibers according to the present invention will be described below.

(1) Sieving of bagasse fibers Bagasse fibers were sieved using mesh 18 (average fiber length: 3.00 mm, average fiber width: 0.4 mm).

(2) Desugarization treatment The filtered bagasse fibers were washed by immersing them in 20 times the weight of the fibers (ion-exchanged water, 80 ° C.) for 10 minutes.
By repeating this twice, the residual sugar contained in the bagasse fiber can be removed.
Then, the bagasse fiber was dried for 24 hours in a constant temperature dryer (forced convection method) at 80 ° C.
It should be noted that this desalination treatment is more effective in desalting by immersing it in hot water (hot water) than in water at room temperature.
Further, in this example, the desalination treatment is performed before the acetylation treatment described later, but it can also be performed after the acetylation treatment, and even in that case, the effect of desalination can be obtained in the same manner.

(3) Pretreatment for acetylation treatment Dried bagasse fibers are immersed in acetic acid (80 ° C.), which is 20 times the weight of the fibers, for 1 hour, and the bagasse fibers taken out from acetic acid are immersed in acetic anhydride at room temperature for 1 minute. rice field.

(4) Acetylation Treatment The bagasse fiber was immersed in acetic anhydride and kept heated to 120 ° C. (hereinafter, this heat treatment is referred to as "acetylation treatment").
"Acetylation" in this example means converting a hydroxyl group into an acetyl group, and catalysts such as pyridine, zinc chloride, sodium acetate, potassium acetate, dimethylformamide, and trifluoroacetic acid can also be used.
Further, if the hydroxyl group of the bagasse fiber can be converted into an acetyl group, in addition to the "acetylation treatment" in this example, various treatments such as esterification, carbamate formation, formalization, epoxidation, aldehyde formation, and inorganic compounding can be performed. Can also be substituted.
The treatment time (heating time) of the acetylation treatment was set to 0, 0.5, 1, 2, 3, and 4 hours in order to investigate the relationship between the heating time and the weight change of the bagasse fiber.

After the acetylation treatment, it was washed with water (ion-exchanged water) and dried in a constant temperature dryer (forced convection method) for 24 hours.
After drying, the weight of the bagasse fiber was measured, and the weight increase rate was calculated from the weight change before and after the acetylation treatment.
The results of weight increase due to the acetylation treatment of bagasse fibers are as follows.

FIG. 1 is a graph showing the rate of weight increase for each heating time of the acetylation treatment.
The vertical axis of the graph shows the weight increase rate of the bagasse fiber, and the horizontal axis shows the heating time.
From this result, it was found that the weight increase rate of the bagasse fiber tends to increase as the heating time is lengthened.
However, the weight increase rate of the bagasse fiber when the heating time is 2 hours is more than 15% as compared with the dried bagasse fiber before the acetylation treatment, but as compared with the case where the heating time is 3 hours and 4 hours. But it turned out that there was no big difference.
Further, the sample "A" in which the pretreatment of the acetylation treatment, that is, the immersion with acetic anhydride at room temperature was made several hours instead of one minute, and the sample "B" in which the heating time of the acetylation treatment was made 21 hours were also obtained. , There was no significant change in the weight increase rate of bagasse fiber.
Since the hydroxyl group in cellulose is replaced with acetyl group by acetylation, it was expected that the weight of bagus fiber would increase due to the difference in molecular weight, but the weight increase rate of bagus fiber even if the heating time exceeds 2 hours. It is presumed that the reason why no change was observed was that all three hydroxyl groups of cellulose were replaced with acetyl groups, resulting in triacetyl cellulose, and no further reaction was possible.
From this result, the heating time in the state where the bagasse fiber is immersed in acetic anhydride, which is necessary for the acetylation treatment of the bagasse fiber (the treatment for substituting the functional group), is required to be 2 hours or more, and 2 to 4 It can be said that the time is appropriate.

(5) Preparation of Composite Pellet The dried bagasse fiber was kneaded with polypropylene pellet in a kneader (temperature 210 ° C., mixing ratio of bagasse fiber and polypropylene was 40 wt%) to prepare a composite pellet.
Although polypropylene was used as the base material for kneading the bagasse fiber in this embodiment, any polyester resin, polyamide resin, or olefin resin can be preferably used.

(6) Preparation of Composite Molding Material The composite pellet was pressed with a press molding machine to prepare a circular composite having a diameter of about 30 mm and a thickness of about 1 mm.
The press was carried out at a temperature of 200 ° C. and a pressure of 50 kgf / cm2 for 1 minute, and then increased to 100 kgf / cm2 for 4 minutes.
Then, it was cooled with water for 5 minutes.
In this embodiment, the composite molding material is produced by hot pressing, but it can also be produced by various methods such as injection molding.

2. The description and test results of each test for the produced composite molded material are as follows.

(1) Surface Roughness Test The change over time with respect to the surface roughness of the composite molded material was observed.
FIG. 2 is a photograph of a composite molding material in which bagasse fibers are only deglycerated and not acetylated, and FIG. 3 is a photograph of a composite molding material in which bagasse fibers are acetylated after being desaccharideted. It is a photograph.
Further, "(A) 0 day" in FIGS. 2 and 3 is a photograph taken on the day of preparation of the composite molded material, and "(B) 7th day" in FIGS. 2 and 3 is the 7th day after the production of the composite molded material. This is a picture taken in (1st week).
The photograph was taken by shining light on the surface of the composite molding material so that the state of the surface could be seen.
It was confirmed that the bagasse fibers were largely exposed on the surface of the composite molded material in which the bagasse fibers were only dessaccharide-treated and not acetylated one week after the production.
On the other hand, the surface of the composite molded material obtained by acetylating the bagasse fiber after the sugar removal treatment did not show a large change even one week after the preparation.
It was clearly confirmed with the naked eye that the uneven deformation of the surface could be suppressed by the acetylation treatment.

FIGS. 4 and 5 are graphs comparing the surface roughness of the composite molded material immediately after production and when immersed in water for 12 weeks after production.
In particular, FIG. 4 shows the results for the composite molded material in which the bagasse fibers were subjected to only the sugar removal treatment and not the acetylation treatment, and FIG. 5 shows the results for the composite molding material in which the bagasse fibers were acetylated after the sugar removal treatment. Is.
As shown in FIG. 4, the surface of the composite molding material obtained by subjecting the bagasse fiber only to the sugar removal treatment and not the acetylation treatment becomes rough when immersed in water for 12 weeks, whereas the bagasse fiber is acetylated after the sugar removal treatment. As shown in FIG. 5, the treated composite molding material had almost no change in surface roughness even when immersed in water for 12 weeks.

FIG. 6 is a graph showing the surface roughness and the water absorption rate for each time elapsed after the composite molding material was immersed in water.
The left vertical axis of the graph shows the surface roughness (Rz), and the right vertical axis shows the water absorption rate.
Based on the results of the composite molding material that has not been acetylated at all (“Acetylation 0h”) and the composite molding material that has been acetylated for 4 hours (“Acetylation 4h”), the surface roughness is roughened by the acetylation treatment. It was found that the roughness (Rz) was about 75% and the water absorption rate was about 58%, respectively.
It is presumed that this is because the hydroxyl group in the cellulose was replaced with an acetyl group by the acetylation treatment, the hydrogen bond by the polymer in the cell wall was suppressed, and the adsorption of water in the cell wall was reduced, so that the water absorption rate was suppressed. ..
In addition, it is said that the surface roughness (Rz) was reduced because the reversible change in the expansion and contraction of the cell wall due to the absorption and desorption of water was reduced, which produced the dimensional stabilization effect of the fiber itself, and at the same time, the occurrence of springback due to water absorption was reduced. Guessed.

(2) Bending test FIG. 7 is a graph showing changes in mechanical properties of the composite molded material over time.
The left vertical axis of the graph shows the flexural modulus, and the right vertical axis shows the bending strength.
The composite molded material was immersed in water immediately after production and tested for mechanical properties after 1 week and 12 weeks.
Based on the results of the composite molding material that has not been acetylated at all (“Acetylation 0h”) and the composite molding material that has been acetylated for 4 hours (“Acetylation 4h”), the acetylation treatment is mechanical. It was found that the deterioration of properties can be suppressed.
However, it was also confirmed that even after the acetylation treatment, the mechanical properties deteriorate when immersed in water for 12 weeks.
As shown in the water absorption test result of FIG. 6, the composite molded material that had been subjected to the acetylation treatment for 4 hours had about 400 hours (about 16 days) after being immersed in water as compared with the composite molded material that had not been subjected to the acetylation treatment. During this period, the water absorption rate has continued to increase by about 6%. Therefore, by acetylating for 4 hours, the fibers expand and spring back due to water absorption until 400 hours have passed since they were immersed in water. Is presumed to have occurred.
It is presumed that this deforms the bagasse fiber and weakens the adhesiveness between the base material (“polypropylene” in this embodiment) and the bagasse fiber, thereby deteriorating the mechanical properties.
However, since the increase in surface roughness (Rz) of the composite molded material that has been subjected to the acetylation treatment for 4 hours is about 75% less than that of the composite molded material that has not been subjected to the acetylation treatment, the bagasse fiber is also deformed. It is presumed that the amount was very small compared to the composite molding material that was not acetylated.
From this, it can be clearly recognized that the deterioration of the mechanical properties is suppressed by the acetylation treatment.

FIG. 8 is a graph showing the effect of different treatments on bagasse fibers on the mechanical properties of the composite molded material.
The differences in the samples (differences in the treatment of bagasse fibers) are as follows.
(A) Composite molding material that has been subjected to only deglycation treatment and not acetylation treatment (B) Composite molding material that has been subjected to acetylation treatment for 4 hours after deglycation treatment (C) After sugar treatment, only alkali treatment is performed. , Composite molding material not subjected to acetylation treatment (D) Composite molding material subjected to acetylation treatment for 4 hours after being subjected to alkali treatment after sugar removal treatment.

The "alkali treatment" in this example is a process in which bagasse fibers and 5% of an aqueous sodium hydroxide solution are mixed at a weight ratio of 1:20, heated at 100 ° C. for 45 minutes, and then washed with water three times. Means.
Since the purpose of the "alkali treatment" is defibration, potassium hydroxide, calcium hydroxide, and sodium carbonate can be substituted in addition to sodium hydroxide.
In addition, a method of crushing, crushing, or blasting with a mechanical force such as a miller or a water jet (for example, after heating and pressurizing a bagus fiber with steam at 180 to 230 ° C for a certain period of time in a pressure cooker, it is instantaneous. A method of opening the valve and discharging it from the kettle together with water vapor) can also be used.

All of (B), (C), and (D) had improved mechanical properties as compared with (A).
Further, in (D), the flexural modulus was increased by about 1.25 times and the bending strength was increased by about 1.5 times, respectively, as compared with (A).
This is because the lignin that is strongly adsorbed between the cellulose fibers is removed by the alkali treatment, and the bagasse fibers are defibrated by defibration, which improves the interfacial adhesion between the bagasse fibers and polypropylene and is mechanical. It can be inferred that the properties have improved.
Since the hydrophilic hydroxyl group is replaced by the hydrophobic acetyl group by acetylation, the affinity for water is lowered and the cohesive force between the bagasse fibers is weakened, which adversely affects the mechanical properties of the bagasse fibers. It is presumed that as a result of the reduction of lumps between the bags, the dispersibility between the bagasse fiber and the polypropylene was increased and the mechanical properties were improved.
Further, it is presumed that the bagasse fibers defibrated by the alkali treatment were hydrophobically modified by the acetylation treatment and uniformly dispersed without agglutination, so that the mechanical properties were further improved.

(3) Microscopic observation FIGS. 9 to 12 show a microscope in which bagasse fibers were subjected to only deglycation treatment and no acetylation treatment was performed, and a composite molding material was immersed in water for 12 weeks after its preparation, and the surfaces were photographed at a plurality of locations. It is a photograph.
From the photograph of FIG. 9, it can be confirmed that the bagasse fiber is not exposed on the surface and the bagasse fiber and polypropylene are adhered to each other, and from the photograph of FIG. 10, the bagasse fiber is exposed on the surface and bagasse. It can be confirmed that a gap is formed between the fiber and polypropylene.
Further, from the photographs of FIGS. 11 and 12, it can be confirmed that one bagasse fiber is torn linearly.
The state shown in the photographs of FIGS. 11 and 12 was caused by the bagasse fibers expanding due to water absorption and being exposed to the surface, and at the same time, the bagasse fibers fixed by polypropylene could not withstand the expanding force and were torn. It is speculated that it may be.
From these observation results, it was found that the bagasse fiber expands when it absorbs water and is exposed on the surface of the composite molding material, which causes an increase in surface roughness.
In addition, it is presumed that the difference in the surface condition was observed depending on the photographed part because the polypropylene was biased during kneading and press molding.
That is, in a place where there is a lot of polypropylene, the surface of the composite molding material is covered with polypropylene to prevent the bagasse fibers from absorbing water, and the expansion of the bagasse fibers is suppressed, so that the bagasse fibers are exposed on the surface as shown in the photograph of FIG. On the contrary, in the place where the amount of polypropylene is small, the bagasse fiber cannot prevent the water absorption of the bagasse fiber, so that the absorbed bagasse fiber expands and the bagasse fiber is exposed on the surface as shown in the photographs of FIGS. 10 to 12. It is presumed.

FIGS. 13 to 16 are photomicrographs of a composite molded material obtained by acetylating bagasse fibers after dessaccharideization treatment, and immersing the composite molding material in water for 12 weeks after its preparation, and taking photographs of a plurality of surfaces thereof.
In the photographs of FIGS. 13 to 16, there are some places where gaps are formed along the bagasse fibers, and it is presumed that this is because the bagasse fibers and polypropylene are separated from each other due to the expansion of the bagasse fibers to form gaps. NS.
Further, in the photograph of FIG. 15, the bagasse fiber was exposed on the surface, but the exposure of the bagasse fiber could not be confirmed in other parts of the photograph of the same figure or in the photographs other than FIG.
Further, from the photographs of FIGS. 13 to 16, the state in which the bagasse fibers were linearly split could not be confirmed, and from the photographs of any of the figures, it was confirmed that the bagasse fibers were adhered to polypropylene.
From these results, the composite molding material obtained by acetylating the bagasse fiber after the sugar removal treatment has expanded the bagasse fiber due to water absorption as compared with the composite molding material in which the bagasse fiber is only subjected to the sugar removal treatment and not subjected to the acetylation treatment. It was found that the bagasse fibers were less exposed on the surface of the composite molding material and the surface roughness of the composite molding material was suppressed.

(4) Odor Sensitivity Test An odor sensory test was conducted to evaluate the odor of the produced composite molding material.
The odor sensory test was carried out based on the criteria in the following three tables: Table 1 (odor intensity display method), Table 2 (pleasure / discomfort degree display method), and Table 3 (odor intensity for each feature).

As the test piece used for the odor sensory test, a composite molded material that had been produced for about 3 weeks and heated according to the following two conditions was used.
(A) The initial test piece was placed in a container, heated at 80 ° C for 1 hour in a closed state with the lid closed, and then cooled to room temperature.
(B) After putting the test piece over time in a container and heating it at 80 ° C for 98 hours with the lid open, closing the container lid to seal it, and then heating it at 80 ° C for another 1 hour. , Cooled to room temperature.

17 and 18 are tables showing the results of the odor sensory test, FIG. 17 shows the test results using the “(a) initial” test piece, and FIG. 18 shows the test results using the “(b) time-lapse” test piece. be.
In each table, "intensity" indicates the evaluation by the odor intensity display method, "pleasant / unpleasant degree" indicates the evaluation by the pleasant / unpleasant degree display method, and "odor characteristic" indicates the evaluation based on the odor intensity for each feature. There is.
In each table, "untreated" is a composite molding material that has not been desalted or acetylated, and "degreased" is a composite that has only been desalted and dried by heating and has not been acetylated. Acetylation-treated vacuum-dried molding material is a composite molding material that is acetylated (heating time is 4 hours) and then vacuum-dried, and "acetylation-treated water-washing → heat-drying" is The composite molding materials obtained by acetylating (heating time: 4 hours) the deglycerated bagus fibers, washing them with water, and drying them by heating are shown.

From this result, it can be seen that "strength" and "pleasantness / discomfort" are all significantly reduced in the order of "untreated", "degreasing treatment", and "acetylation treatment".
In addition, the "odor characteristic" was that the "untreated" had a very sweet brown sugar-like odor, which was an unpleasant odor that caused nausea as a whole. The sweet odor and nauseous odor were alleviated, and the "acetylation treatment" reduced the overall odor including the sweet odor, but a slight pungent odor was felt.
However, from the results of "acetylation treatment washing with water → heat drying", it was confirmed that the pungent odor disappeared by washing the bagasse fibers with water after the acetylation treatment.

Bagasse fibers contain 48% cellulose, 25% hemicellulose, and 12% lignin, respectively. The thermal decomposition temperatures of these are 315 to 400 ° C for cellulose, 160 to 900 ° C for hemicellulose, and 220 to 315 ° C for lignin. Since the temperature at the time of molding the composite molding material is about 200 ° C to 220 ° C, it is considered that hemicellulose and lignin may be thermally decomposed at the time of molding.
Hemicellulose is pyrolyzed to xylose, arabinose, glucose, hydroxymethylfurfural, furfural, which can cause a sweet odor.
When lignin is thermally decomposed, it becomes methoxyphenol and its derivatives guaiacol and guaiacol, but syringol and guaiacol may cause blackening and a burning odor due to the generation of charring during molding.
It is probable that hemicellulose and lignin released the components that cause the odor by thermal decomposition, which caused the sweet odor and burnt odor to be felt in the test piece of the "degreasing treatment".
Bagasse fibers have hydrophilic properties because they have hydroxyl groups in cellulose and hemicellulose, so they absorb moisture in a short time during kneading and pressing after drying, and during molding, the water adsorbed on the cell wall becomes vapor and heat. It is presumed that the decomposition may have been promoted.
In addition, the hydroxyl group in the bagasse fiber was replaced with an acetyl group by the acetylation treatment, and the hydrophobic denaturation suppressed the adsorption of water and suppressed the promotion of thermal decomposition by steam, resulting in a sweet odor and a burnt odor. It is speculated that it may have been alleviated.
In addition, the pungent odor generated by the acetylation treatment was alleviated by washing with water after the acetylation treatment, and it is considered that the acetic acid component used in the acetylation treatment remained in the bagasse fiber. ..

3. 3. Summary As described above, the following results were obtained by acetylating the bagasse fiber.
A maximum of about 58% of water absorption suppressing effect can be obtained, and an increase in surface roughness (Rz) of the composite molded material over time is suppressed (up to about 75%).
Deterioration of mechanical properties over time is suppressed, and if acetylation treatment is performed after alkali treatment, a further effect of improving mechanical properties can be obtained.
The odor of the molded product of the composite molded material of bagasse fiber and polypropylene is alleviated by performing the acetylation treatment stepwise after the sugar removal treatment, and further, the irritating odor can be suppressed by washing the bagasse fiber with water after acetylation.
Therefore, by acetylating the bagasse fiber, it is possible to suppress water absorption without impairing the physical properties of the conventional bagasse fiber composite material, so that the surface of the composite molded material molded body can be kept smooth while maintaining a smooth surface. Since the sweet odor peculiar to sugar cane can be significantly reduced, it can be used for interior parts of automobiles, for example.

(Example 2)
1. 1. A method for producing a composite molded material using bagasse fibers according to the present invention will be described below.

(1) Sieving of bagasse fibers Bagasse fibers were sieved using mesh 18 (average fiber length: 3.00 mm, average fiber width: 0.4 mm).

(2) Drying treatment The bagasse fibers were dried at a constant temperature dryer (forced convection method) at 80 ° C.
In order to examine the rate of weight increase due to the drying time, the drying time was appropriately changed.

(3) The deglycerated bagasse fiber was washed by immersing it in 20 times the weight of the fiber (ion-exchanged water, 80 ° C.) for 10 minutes.
Thereby, the residual sugar contained in the bagasse fiber can be removed.

(4) Pretreatment of Acetylation Treatment The deglycerated bagasse fiber was immersed in acetic anhydride in an amount 20 times the weight of the fiber for 1 minute.
(5) Acetic anhydride was removed from the bagasse fiber using an acetylated bamboo basket, and the bagasse fiber was soaked with acetic anhydride and heated in an oil bath (120 ° C.).
In order to investigate the effect of the heating time on the weight increase, the heating time was appropriately changed.
In addition, pyridine can be used together with acetic anhydride for the acetylation treatment, and in that case, the heating temperature can be lowered.
Pyridine is sufficiently effective even at an addition ratio of about 1.0% or less, but if the addition ratio is small, a long heating time until acetylation is required.

(6) Washing treatment After the acetylation treatment, the bagasse fibers were washed with ion-exchanged water and dried in a constant temperature dryer (forced convection method) for 24 hours.

(7) Soaking in hot water The dried bagasse fibers are immersed in ion-exchanged water at 80 ° C. for up to 2 hours to remove acetic anhydride remaining on the bagasse fibers, and then dried in a constant temperature dryer (forced convection method) for 24 hours. I let you.

The weight of the bagasse fiber after drying was measured, and the weight increase rate was calculated based on the weight change before and after the acetylation treatment.
The weight increase rate is calculated by the following formula.
W ₁ = ((W _after −W _before ) / W _before ) × 100 (%)
W ₁ : Weight increase rate (%)
W _after : Weight of bagasse fiber after acetylation treatment (g)
W _before : Weight of bagasse fiber before acetylation treatment (g)

(8) Preparation of Composite Pellet The dried bagasse fiber was kneaded with polypropylene pellet in a kneader (temperature 200 ° C., mixing ratio of bagasse fiber and polypropylene was 40 wt%) to prepare a composite pellet.
Although polypropylene was used as the base material for kneading the bagasse fiber in this embodiment, any polyester resin, polyamide resin, or olefin resin can be preferably used.

(9) Preparation of Composite Molding Material The composite pellet was pressed with a press molding machine to prepare a circular composite having a diameter of about 30 mm and a thickness of about 1 mm.
The press was performed at a temperature of 200 ° C. and a pressure of 100 kgf / cm ² for 5 minutes, and then cooled with water for 5 minutes.
In this embodiment, the composite molding material is produced by hot pressing, but it can also be produced by various methods such as injection molding.

The composite produced in the above step was cut into a rectangular shape having a width of about 15 mm, and the strength was evaluated by a three-point bending test.
The measured value of bending stress was calculated by the following formula.
The bending stress of the rectangular cross-section test piece is shown below.
σ ＝ 3F _max L / 2bh ³
L is the distance between fulcrums (21 mm), and b and h are the width and thickness of the produced composite.
F _max is the maximum load immediately before rupture.
The measured value of flexural modulus was calculated by the following formula.
The flexural modulus when a one-point concentrated load is applied to the center of the simple support beam is shown below.
E = (L ³ / 4bh ³ ) × (ΔF / ΔS)
ΔF: Load increase amount ΔS: Displacement increase amount

2. The description and test results of each test for the produced composite molded material are as follows.

(1) Drying Experiment In FIG. 19, bagasse fibers that have not been acetylated are dried in a constant temperature dryer (80 ° C.), and the rate of decrease in water content over time (= {(weight before drying-weight after drying) ÷ It is a graph showing the dry weight before drying} × 100).
The vertical axis of the graph shows the reduction rate of the water content in the bagasse fiber, and the horizontal axis shows the drying time.
It was found that after drying for 12 hours, the water content in the total weight of the bagasse fiber was reduced by 10%.
In addition, 8% of the total weight of water decreased by 1 hour after the start of drying.

(2) Acetylation reaction rate of bagus fiber for each drying time FIG. 20 shows acetylation using bagas fiber dried for a maximum of 6 hours every hour for the first drying time and bagus fiber dried for 12 hours. The acetylation treatment time was fixed at 2 hours, and the weight increase rate of each drying time (= {(dry weight after acetylation treatment-dry weight before acetylation treatment) ÷ dry weight before acetylation} × 100) was measured. It is a graph showing the result of the above.
In the sample used for this measurement, the desalination treatment is performed at the same time as the washing treatment after the acetylation treatment.
The vertical axis of the graph shows the weight increase rate, and the horizontal axis shows the drying time.
The weight increase rate of the undried bagasse fiber was 2.25%, which was lower than the others.
It is considered that this is because the water in the bagasse fiber reacted with acetic anhydride and acetylation was inhibited by immersing the bagasse fiber in acetic anhydride in an undried state.
There was no change of 1% or more in the weight increase rate with respect to the bagasse fiber dried for 1 hour or more.
It is considered that this is because there was no significant difference in the amount of water contained in the bagasse fibers dried for 1 hour or more, based on the measurement results of the drying experiment in (1) above.

(3) Weight change of bagasse fiber for each acetylation treatment time After drying the bagasse fiber for 12 hours, the weight of the result of acetylation treatment for up to 6 hours every hour and for another 6 hours (12 hours in total). I investigated the changes.
FIG. 21 is a graph showing the results of measuring the weight increase rate of bagasse fibers for each acetylation treatment time by performing the desalination treatment at the same time as the washing treatment in the same manner as in the experiment (2) above.
The vertical axis of the graph shows the rate of weight increase, and the horizontal axis shows the acetylation treatment time.
The rate of weight increase tends to increase as the acetylation treatment time increases.
It is considered that the weight is increased by substituting the hydroxyl groups in the cellulose contained in the bagus fiber with acetyl groups by the acetylation treatment, but the weight increase rate is 1.25 after the treatment time of 4 hours. It is presumed that the reason why the change of% or more is not seen is that all the hydroxyl groups in the cellulose are replaced with acetyl groups.
The difference between the 12-hour weight gain rate and each weight gain rate from 2 hours to 6 hours was within 2.25%.
From this result, it was found that the weight increase rate of the bagasse fiber subjected to the acetylation treatment for 2 hours or more did not change significantly even if the desalination treatment was performed at the same time as the washing treatment.

(4) Changes in Mechanical Properties of Composite for Each Odor Control Treatment Process FIG. 22 is a graph comparing changes in mechanical properties of composite molding materials (Samples 1 to 3) that differ for each odor control treatment process. ..
The left vertical axis of the graph shows the flexural modulus, the right vertical axis shows the bending strength, and the horizontal axis shows the sample.
Each processing process of samples 1 to 3 is as follows.
Sample 1: Acetylation treatment only Sample 2: Acetylation treatment after acetylation treatment Sample 3: Acetylation treatment after acetylation treatment

Sample 1 was subjected to only deglycation treatment, sample 2 was subjected to acetylation and hot water pickling treatment after acetylation treatment, and sample 3 was subjected to sugar removal treatment and hot water pickling treatment after acetylation.
The acetylation treatment (heating for 4 hours) and the desalination treatment were carried out under the same conditions for all the samples.
The "degreasing treatment" in the test of FIG. 22 means that the bagasse fiber was immersed in ion-exchanged water (80 ° C.) having a weight ratio of 20 times in hot water three times (30 minutes each time).
As is clear from FIG. 22, the mechanical properties of Sample 2 and Sample 3 were higher than those of Sample 1.
It is considered that this is because the cellulose contained in the bagasse fiber was modified by the acetylation treatment and changed to acetyl cellulose.
That is, it is presumed that the interfacial adhesive strength between the acetylated bagasse fiber and the hydrophobic polymer such as polypropylene was higher than that of the hydrophilic bagasse fiber.
It is not clear why the first acetylated sample of sample 3 had higher mechanical properties than the acetylated sample 2 after the desalination treatment, but water-soluble solubles such as sucrose were acetylated and then It is presumed that it remained in the bagasse fiber even after the hot water pickling treatment performed in the above, and for some reason, it led to the improvement of the interfacial adhesion between polypropylene and the bagasse fiber.

(5) Microscopic observation of the composite surface FIGS. 23 to 25 are photographs of the surface state of the composite molding material of the sample 1 of the experiment of the above (4) taken with a microscope.
No part of the bagasse fiber was exposed on the surface, and it was confirmed that the bagasse fiber and polypropylene were adhered to each other.
In addition, the amounts of bagasse fiber and polypropylene differed depending on the place of observation.
It is considered that this is because the melted polypropylene flowed into the part where the bagasse fibers were scarce during press molding and was molded.
26 to 28 are photographs taken with a microscope of the surface state of the composite molded material of the sample 3 of the experiment of the above (4).
Similar to Sample 1, no part where the bagasse fiber was exposed on the surface was observed, and it was confirmed that the bagasse fiber and polypropylene were adhered to each other.
Further, as in the case of sample 1, the amounts of bagasse fiber and polypropylene were different depending on the place of observation.

(6) Odor Sensitivity Test An odor sensory test was conducted to evaluate the odor of the produced composite molding material.
The odor sensory test was carried out based on the criteria of the three tables of Table 1 (odor intensity display method), Table 2 (pleasant / unpleasant degree display method), and Table 3 (odor intensity for each feature) according to Example 1. ..
The test pieces used for the odor sensory test were polypropylene only, acetylated untreated bagasse fibers, and composite samples using bagasse fibers for each treatment process, which were heated at 80 ° C for 98 hours. Was placed in a container, sealed with a lid, heated at 80 ° C. for 1 hour, returned to room temperature, and then an odor sensory test was conducted.

FIGS. 29 to 33 are tables showing the results of the odor sensory test.
The composite molded material made only of polypropylene in FIG. 29 had a value of 0 (odorless) in all of odor strength, pleasantness / discomfort, and odor characteristics.
In the composite using the untreated bagasse fiber of FIG. 30, the odor intensity was 1.81, which was the highest value in the odor sensory test.
It is considered that the odor intensity value was the highest because the sugar content remained in the bagasse fiber without performing the sugar removal treatment or the acetylation treatment.
FIG. 31 shows the results of an odor sensory test of a composite made of defatted bagasse fiber.
By performing the sugar removal treatment, the odor intensity value was 0.54 times higher than that of the untreated bagasse fiber composite shown in FIG. 30.
FIG. 32 is the odor sensory test result of the bagasse fiber composite subjected to the odor suppression treatment of Example 1, and FIG. 33 is the odor sensory test result of the bagasse fiber composite subjected to the odor suppression treatment of Example 2.
Both FIGS. 32 and 33 showed an odor intensity of 1 or less and a sweetness of 0.1 or less in terms of odor characteristics by subjecting the acetylation treatment.
From this result, it was found that the sweet odor peculiar to bagasse was alleviated by the acetylation treatment.
Further, from the results of FIG. 33, it can be said that the bagasse fiber composite of Example 2 has an odor strength of 0.17, a pleasant / unpleasant degree of 0, and an odor characteristic of 0 other than charring, and is almost odorless.

3. 3. Summary The smaller the amount of water contained in the bagasse fiber, the higher the rate of weight increase when the acetylation treatment is applied.
Even if the desglycation treatment was performed at the same time as the washing treatment, the weight increase rate did not change by 2.25% or more after 2 hours of the acetylation treatment, so that the acetylation treatment time of about 2 hours is sufficient.
By performing the desalination treatment after the acetylation treatment, the elastic modulus was increased.
Even if the degassing treatment was performed at the same time as the hot water dipping treatment without the washing treatment and the second drying treatment, the bending strength did not change by 1.7 MPa or more.
From the results of the odor sensory test, the odor of the composite material obtained by the treatment process of Example 2 was suppressed as compared with that of the composite material obtained by the treatment process of Example 1.
From the above results, the bagasse fiber composite material obtained by the treatment process of Example 2 can suppress the odor without impairing the physical properties of the bagasse fiber composite material by the treatment process of Example 1, and the living space and people can be affected. It can also be used for touching products (for example, building materials and interior parts of automobiles).

Claims (2)

After converting the hydroxyl group of the bagasse fiber into an acetyl group, the bagasse fiber is immersed in water for sugar removal and washing, kneaded with polypropylene, and the composite is injection-molded or hot-pressed to maintain the smoothness of the surface. A method for producing a composite molded material using bagasse fiber, which is characterized in that a composite molded material in which the sweet odor peculiar to sugar cane is significantly reduced can be obtained. The bagasse fiber is heated for 2 hours or more in a state of being immersed in anhydrous acetic acid to convert the hydroxyl group of the bagasse fiber into an acetyl group, then immersed in water for sugar removal and washing, and kneaded with polypropylene to form a composite. A method for producing a composite molded material using bagasse fibers, which is characterized by being able to obtain a composite molded material in which the sweet odor peculiar to sugar cane is significantly reduced while maintaining the smoothness of the surface by injection molding or heat pressing. ..

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