Molding material, manufacturing method of molding material, and manufacturing method of pulp molded product

Abstract

To provide a molding material that can achieve a pulp molding having transparency, a method for producing the molding material, and a method for producing the pulp molding.SOLUTION: A molding material is predominantly composed of pulp and a starch binder. The pulp includes conifer pulp. The component ratio (by weight) of the pulp to the starch binder is 3:7 to 6:4.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a molding material, a method for producing a molding material, and a method for producing a molded pulp product. [Background technology]

[0002] The applicant has been focusing on the development of pulp injection molding, a new molding technology that uses molding materials whose main components are pulp and starch-based binders, as an alternative to plastics, and has filed many patent applications relating to molding materials and manufacturing methods related to pulp injection molding, as well as molded products using these technologies (e.g., Patent Documents 1 to 3). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 2916136 [Patent Document 2] Patent No. 4716969 [Patent Document 3] Patent No. 6697874 Summary of the Invention [Problem to be solved by the invention]

[0004] However, conventional pulp injection molding technology has not been able to make pulp molded products transparent, and it has not been possible to provide pulp molded products as replacements for plastic molded products that require transparency so that the inside of the container can be checked, such as disposable syringes.

[0005] The present invention has been developed in consideration of the current state of pulp molded products, and provides a molding material that enables the realization of pulp molded products with transparency (light transmittance), a manufacturing method thereof, and a manufacturing method for pulp molded products. [Means for solving the problem]

[0006] The gist of the present invention will now be described with reference to the accompanying drawings.

[0007] The present invention relates to a molding material whose main components are pulp and a starch-based binder, wherein the pulp contains coniferous pulp, and the component ratio (by weight) of the pulp to the starch-based binder is 3:7 to 6:4.

[0008] The present invention also relates to a molding material according to claim 1, characterized in that the pulp is softwood pulp and hardwood pulp.

[0009] The molding material according to claim 2 is characterized in that the component ratio (by weight) of the softwood pulp, the hardwood pulp, and the starch-based binder is 3:3:4 to 1.5:4.5:4.

[0010] The present invention also relates to the molding material described in claim 3, characterized in that the content of the starch-based binder is 30 wt % to 40 wt %.

[0011] The molding material according to any one of claims 2 to 4 is characterized in that the softwood pulp has a fiber length of about 2 mm and a fiber diameter of about 40 μm, and the hardwood pulp has a fiber length of about 0.9 mm and a fiber diameter of about 20 μm.

[0012] The present invention also relates to a method for producing a molding material whose main components are pulp and a starch-based binder, which includes a mixing step of mixing the pulp, the starch-based binder and water, and a kneading step of kneading the mixture obtained by the mixing step, wherein the mixing step uses at least softwood pulp as the pulp, and further, the mixing ratio (by weight) of the pulp to the starch-based binder is 3:7 to 6:4.

[0013] The method for producing a molding material according to claim 6 is characterized in that the mixing step uses softwood pulp and hardwood pulp as the pulp.

[0014] In addition, in the method for producing a molding material described in claim 7, the mixing step is characterized in that the mixing ratio (by weight) of the softwood pulp, the hardwood pulp and the starch-based binder is 3:3:4 to 1.5:4.5:4.

[0015] Further, in the method for producing a molding material according to any one of claims 6 to 8, the mixing step is characterized in that the mixing ratio of the water to the molding material is 10 wt% to 15 wt%.

[0016] The method for producing a molding material according to any one of claims 6 to 9 relates to a method for producing a molding material, characterized in that a non-alkali metal salt of a long-chain fatty acid is added to the mixture.

[0017] In addition, in the method for producing a molding material described in claim 10, the addition of the non-alkali metal long-chain fatty acid salt is 0.2 wt% to 2.0 wt% relative to 100 wt% of a mixture of the pulp, the starch-based binder, and water.

[0018] Furthermore, in the method for producing a molding material described in any one of claims 6 to 11, the softwood pulp has a fiber length of about 2 mm and a fiber diameter of about 40 μm, and the hardwood pulp has a fiber length of about 0.9 mm and a fiber diameter of about 20 μm.

[0019] The method for producing a molding material according to any one of claims 6 to 12 relates to a method for producing a molding material, characterized in that the kneading step kneads the mixture under the following conditions: Note Temperature: 60℃~100℃ Mixing speed: 80 rpm to 120 rpm Mixing time: 5 minutes or more

[0020] The present invention also relates to a method for producing a pulp molded product whose main components are pulp and a starch-based binder, characterized in that the molding material shown in 1 below is compression molded under the press conditions shown in 2 below. Note 1 A molding material containing pulp and a starch-based binder as main components, the pulp including softwood pulp, and a component ratio (by weight) of the pulp to the starch-based binder of 3:7 to 6:4. Note 2 Press pressure: 2 tons to 4 tons Press temperature: 80℃~100℃ Press time: 1 to 5 minutes

[0021] The present invention relates to a method for producing a molded pulp product, characterized in that the molding material contains softwood pulp and hardwood pulp as the pulp.

[0022] In addition, in the method for producing a pulp molded product described in claim 15, the molding material is characterized in that the component ratio (by weight) of the softwood pulp, the hardwood pulp, and the starch-based binder is 3:3:4 to 1.5:4.5:4.

[0023] The present invention also relates to a method for producing a pulp molded product, characterized in that the molding material is injection molded and the injection molded product is compression molded under the above conditions, in the method for producing a pulp molded product described in any one of claims 14 to 16. Effect of the Invention

[0024] Since the present invention is configured as described above, it provides a molding material that makes it possible to realize a pulp molded product having transparency (light transmittance), a manufacturing method thereof, and a manufacturing method of a pulp molded product. [Brief description of the drawings]

[0025] [Figure 1] 1 shows an example of criteria for evaluating the transparency of this embodiment. [Diagram 2] 1 is a table showing molding conditions for a light transmittance evaluation test in this embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] A preferred embodiment of the present invention will be briefly described below with reference to the drawings to illustrate the operation of the present invention.

[0027] The molding material of the present invention is mainly composed of pulp and a starch-based binder, and the pulp is a mixture of softwood pulp and hardwood pulp.

[0028] The fiber diameter and fiber length of softwood pulp and hardwood pulp are different, with hardwood pulp being thinner and shorter. Therefore, when this mixed pulp is mixed with a starch-based binder, the hardwood pulp penetrates into the gaps in the softwood pulp and fills them, reducing the porosity of the molding material and resulting in a molding material that is less likely to produce bubbles during molding.

[0029] Therefore, pulp molded products that are injection molded or compression molded using the molding material of the present invention have almost no air bubbles in the molded product (inside the part), and light reflection and scattering due to air bubbles is reduced, resulting in improved light transmittance and transparency.

[0030] As a result, by using the molding material of the present invention, it is possible to provide molded pulp products that require transparency so that the inside of the container can be checked, something that was not possible before, such as disposable syringes. EXAMPLES

[0031] A specific embodiment of the present invention will now be described with reference to the drawings.

[0032] This example is a pulp molded product (pulp compression molded product) having transparency (light transmittance) obtained by compression molding a molding material containing pulp and a starch-based binder as main components under predetermined conditions.

[0033] First, a molding material and a manufacturing method thereof according to the present embodiment will be described.

[0034] The molding material of this embodiment is composed mainly of pulp and a starch-based binder, and specifically, is a mixture of pulp, a starch-based binder, and water, to which a non-alkali metal long-chain fatty acid salt is added and kneaded, and then molded into a predetermined shape (e.g., pellet shape).

[0035] In detail, the pulp used is made of softwood pulp and hardwood pulp. The softwood pulp has a fiber length of about 2 mm and a fiber diameter of about 40 μm, while the hardwood pulp has a fiber length of about 0.9 mm and a fiber diameter of about 20 μm.

[0036] The mixing ratio of these is softwood pulp: hardwood pulp=1:1 to 1:3 (preferably softwood pulp: hardwood pulp=1:1).

[0037] In addition, the component ratio (by weight) of the entire pulp (coniferous pulp and hardwood pulp) to the starch-based binder is 6:4, and as a result, the component ratio (by weight) of the coniferous pulp, hardwood pulp, and starch-based binder is coniferous pulp:hardwood pulp:starch-based binder = 3:3:4 to 1.5:4.5:4.

[0038] Corn starch is used as the starch-based binder, but other starch-based binders such as potato starch and rice flour may also be used.

[0039] Moreover, the amount of water added to the mixture of the softwood pulp, hardwood pulp, and starch-based binder is 10 wt % to 15 wt % (preferably 13 wt % or more) of the molding material.

[0040] Therefore, the overall component ratio of the molding material in this embodiment is pulp: 50wt% to 60wt%, starch-based binder: 30wt% to 40wt%, and water: 10wt% to 15wt%.

[0041] In addition, the molding material of this embodiment is obtained by mixing a suitable ratio of 50 wt% to 60 wt% of mixed pulp, which is a 1:1 to 1:3 mixture of softwood pulp and softwood pulp, and 30 wt% to 40 wt% of a starch-based binder (corn starch), adding a suitable amount of water of 10 wt% to 15 wt% to this mixture, adding an appropriate amount (in this embodiment, 0.2 wt% to 2 wt% per 100 wt% of the mixture) of a non-alkali metal long-chain fatty acid salt, adding 30 wt% to 35 wt% of water per 100 wt% of the mixture to which the non-alkali metal long-chain fatty acid salt has been added, kneading the mixture, and then molding it into a pellet shape.

[0042] The kneading conditions in this example are as follows: temperature: 60° C. to 100° C., kneading speed: 80 rpm to 120 rpm, and kneading time: 5 minutes or more.

[0043] Next, a manufacturing (molding) method of this embodiment using the above molding material will be described.

[0044] This embodiment is obtained by compression molding the above-mentioned molding material under the following press conditions: pressure: 1 ton to 5 tons (preferably 2 tons to 4 tons), pressure temperature: 60°C to 100°C (preferably 80°C to 100°C), pressure time: 1 minute to 5 minutes (preferably 2 minutes to 4 minutes).

[0045] Specifically, the set thickness during molding (the thickness of the gap when the spacer is inserted and pressed down) is set to 0.1 mm to 0.3 mm (preferably 0.2 mm to 0.3 mm).

[0046] Alternatively, the molding material may be injection molded, and the injection molded product may be compression molded as described above.

[0047] In addition, from the results of the evaluation tests described below, it has been confirmed that the optimal mixing ratio (by weight) of softwood pulp, hardwood pulp, starch-based binder and water in the molding material is softwood pulp: hardwood pulp: starch-based binder: water = 26:26:35:13, and that the optimal molding conditions (press temperature and set thickness) when molding a molded product using this molding material are press temperature: 100°C and set thickness: 0.2 mm.

[0048] Under the above conditions, a pulp molded product having the desired durability and transparency was obtained.

[0049] The pulp molded product of this embodiment is made by compression molding, under the appropriate conditions described above, a molding material consisting of a mixture of softwood pulp and hardwood pulp in a mixing ratio of 1:1 to 1:3. This prevents air bubbles from being generated in the molded product (and therefore no interface is formed). This results in a pulp molded product with good transparency (light transmittance) with an unprecedented light transmittance. Because it has such good transparency, it can now be used as a replacement for pulp molded products in items that require transparency to check the inside of the container, such as disposable syringes, and lighting fixture covers (shades), which could not be replaced by pulp molded products until now, thereby promoting the move away from plastic.

[0050] Next, a transparency evaluation test and a light transmittance evaluation test that support the above-mentioned effects of this embodiment (the mixture ratio of the molding materials according to this embodiment and the set values ​​of the molding conditions for the pulp molded product) will be described.

[0051] <Transparency evaluation test> In the transparency evaluation test, five types of molding materials were created by changing the mixing ratio of softwood pulp, hardwood pulp, and starch-based binder as shown in Table 1, and the following changes were confirmed: (1) Changes in transparency due to differences in temperature (press temperature) during molding, (2) Changes in transparency due to differences in set thickness during molding, and (3) Changes in transparency due to differences in moisture content of the molding materials.

[0052] [Table 1]

[0053] (1) Transparency evaluation test according to molding temperature (press temperature) In this test, each molding material shown in Table 1 was mixed with water so that the moisture content was 13 wt%, and compression molded (press molded) under molding conditions of press temperatures of 60°C, 80°C, and 100°C (set thickness: 0.2 mm, press pressure: 4 tons, press time: fixed at 2 minutes), and the transparency of each resulting molded product was evaluated.

[0054] The transparency was judged based on the criteria shown in Figure 1. As shown in Figure 1, the criteria were as follows: ◯: the lines and letters of the background were clearly visible; △: the lines and letters of the background were visible, although there was some cloudiness; ×: the lines and letters of the background were difficult to see.

[0055] The results of this test are shown in Table 2. As shown in Table 2, in the case of molding materials (Examples 1 and 2) using both softwood pulp and hardwood pulp as the pulp components, molded articles having good transparency were obtained at 100° C. Furthermore, in the molding materials of this example, Example 1 (a 1:1 mixture of softwood pulp and hardwood pulp) produced molded articles that were slightly cloudy but had transparency at a press temperature of 80° C.

[0056] [Table 2]

[0057] (2) Transparency evaluation test based on thickness setting during molding In this test, each molding material shown in Table 1 was mixed with water so that the moisture content was 13 wt%, and compression molded (press molded) under molding conditions with set thicknesses of 0.1 mm, 0.2 mm, and 0.3 mm (press temperature: 100°C, press pressure: 4 tons, press time: fixed at 2 minutes). The transparency of each molded product obtained was judged based on the judgment criteria shown in Figure 1, as in the transparency evaluation test based on the molding temperature (press temperature).

[0058] The results of this test are shown in Table 3. As shown in Table 3, in this evaluation test, good transparency was confirmed only in the molded articles using the molding material of this example. In addition, in the molding material of this example, this example 1 (a mixture ratio of softwood pulp and hardwood pulp of 1:1) gave molded articles with good transparency under all thickness conditions.

[0059] [Table 3]

[0060] (3) Transparency evaluation test based on the moisture content of molding materials In this test, molding materials with moisture contents of 10wt%, 12wt%, and 13wt% were prepared for each molding material shown in Table 1, and these were compression molded under the molding conditions of set thickness: 0.2mm, press temperature: 100℃, press pressure: 4 tons, and press time: 2 minutes. The transparency of each molded product obtained was judged based on the judgment criteria shown in Figure 1, as in the transparency evaluation test based on the molding temperature (press temperature).

[0061] The results of this test are shown in Table 4. As shown in Table 4, good transparency was confirmed only in the molded articles using the molding material of this example. In addition, among the molding materials of this example, this example 1 (a 1:1 mixture of softwood pulp and hardwood pulp) gave molded articles with good transparency under all moisture content conditions.

[0062] [Table 4]

[0063] <Light transmittance evaluation test> In this test, the molding material of this example (a molding material with a mixing ratio of softwood pulp: hardwood pulp: starch = 30: 30: 40, moisture content of 13wt% to 14wt%) was used to create 12 molded products (No. 1 to No. 12) with different molding conditions of set wall thickness, press pressure and press time as shown in Table 5, and the light transmittance of each molded product was measured to confirm the change in light transmittance (transparency) due to the difference in molding conditions. Note that the press temperature was fixed at 100°C as a molding condition.

[0064] [Table 5]

[0065] The results of this test are shown in Figure 2. As shown in Figure 2, it was confirmed that the light transmittance is highly dependent on the set wall thickness in the molding conditions, and the thinner the set wall thickness, the higher the light transmittance (the more transparent the material is).

[0066] In this test, similar to the transparency evaluation test, the transparency of each molded product was judged based on the criteria in Figure 1. As a result, all of No. 1 to No. 12 were judged to have good transparency, with a rating of ◯.

[0067] From the above, it is found that the most desirable molding material is one in which the mixing ratio of mixed pulp to starch-based binder is 6:4, the mixing ratio of softwood pulp to hardwood pulp in the mixed pulp is 1:1, and the moisture content of the molding material is 13 wt%. By compression molding this molding material at a press pressure of 4 tons, a press temperature of 100°C, and a set thickness of 0.2 mm, the pulp molded product will have the greatest transparency.

[0068] It should be noted that the present invention is not limited to the present embodiment, and the specific configuration of each component can be designed as appropriate.

Claims

1. A molding material comprising softwood pulp, hardwood pulp and a starch-based binder, wherein the component ratio (by weight) of said softwood pulp, said hardwood pulp and said starch-based binder is 3:3:4 to 1.5:4.5:4, and further wherein the content of said starch-based binder is 30 wt% to 40 wt%.

2. 2. The molding material according to claim 1, wherein the softwood pulp has a fiber length of 2 mm and a fiber diameter of 40 μm, and the hardwood pulp has a fiber length of 0.9 mm and a fiber diameter of 20 μm.

3. A method for producing a molding material using softwood pulp, hardwood pulp and a starch-based binder, comprising a mixing step of mixing the softwood pulp, the hardwood pulp, the starch-based binder and water, and a kneading step of kneading the mixture obtained by the mixing step, wherein the mixing ratio (by weight) of the softwood pulp, the hardwood pulp and the starch-based binder is 3:3:4 to 1.5:4.5:4, and further wherein the content of the starch-based binder is 30 wt% to 40 wt%.

4. 4. The method for producing a molding material according to claim 3, wherein the mixing step is performed with the water at a mixing ratio of 10 wt % to 15 wt % of the molding material.

5. 5. The method for producing a molding material according to claim 3, wherein the mixture further contains a non-alkali metal salt of a long-chain fatty acid.

6. 6. The method for producing a molding material according to claim 5, wherein the non-alkali metal long-chain fatty acid salt is added in an amount of 0.2 wt % to 2.0 wt % relative to 100 wt % of a mixture of the softwood pulp, the hardwood pulp, the starch-based binder and the water.

7. The method for producing a molding material according to any one of claims 3 to 6, characterized in that the softwood pulp has a fiber length of 2 mm and a fiber diameter of 40 μm, and the hardwood pulp has a fiber length of 0.9 mm and a fiber diameter of 20 μm.

8. 8. The method for producing a molding material according to claim 3, wherein the kneading step kneads the mixture under the following conditions: Note Temperature: 60℃~100℃ Mixing speed: 80 rpm to 120 rpm Mixing time: 5 minutes or more

9. A method for producing a pulp molded product using softwood pulp, hardwood pulp and a starch-based binder, characterized in that the molding material specified in 1 below is compression molded under the press conditions specified in 2 below. Note 1 A molding material in which the component ratio (by weight) of softwood pulp, hardwood pulp and starch-based binder is 3:3:4 to 1.5:4.5:4, and the content of the starch-based binder is 30 wt % to 40 wt %. Note 2 Press pressure: 2 tons to 4 tons Press temperature: 80℃ to 100℃ Press time: 1 to 5 minutes

10. 10. The method for producing a molded pulp product according to claim 9, further comprising injection molding said molding material, and compression molding said injection molded product under said press conditions.

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