事業展開
　弊社では、高い品質を常に追い求めています。その過程で材料の開発実験も実施しております。
　以下に弊社で実施した実験の一例を紹介します。


高強度パルプの材料開発
１　序論
２　従来技術
３　問題点
４　解決のための対策
５　操作
　　１　異なった材料の物質的比較
　　２　濾過度と物質的性質の関係
　　３　繊維の長さ分布
　　４　音の特製
６　結論
（要約：　スピーカーのための材料として、あらゆる合成繊維が使用されています。この研究では、最も良い材料として木材パルプを使い、日本特有の製紙技術に戻ることで、繊維を断ち切らず従来型のものよりも強く弾性の強い数値を得ました。これを基に、より良い物理的性質、音の品質、スピーカー用途にあわせるための、材料のよりよい組み合わせと、製造技術の方法を計画しています）

1. Development of material for sun-proofed cone paper

Development goal: The development of raw materials aims at having a property of strong sun-proof for cone body that are using a loudspeakers for public address system and/or car audio or the like.

The followings are result of comparative experiments between developed material and toughness material in existing use.

 

1-1. Test samples

              Sample ①           Material: UNKP

                                          Freeness: 500cc (Beaten by Niagara style beater)

                                          Dyestuff: Black L (by Nippon Kayaku Co., Ltd.)

              Sample ②           Material: No.5800 (Developed material for sun-proof)

                                          Freeness: 500cc (Beaten by Niagara style beater)

                                          Color: Black

 

1-2. Exposure test devise

              Ultraviolet lamp  : Length 300mm / Output power

              Test box size: W×L×H= 300×500×300mm

              Irradiation distance: 300mm from the lamp

              Irradiation time: 0 to 250 hrs (sampling by every 50hrs)

It’s terminated the experimental test at the point of beginning of color fading with regard to the sample that will be irradiated ultraviolet over 250hrs. And the degree of color fading, it’s judged at the point of the out view getting close to sample① that was irradiated ultraviolet over 250hrs.

 

1-3. The result of physical property

1-3-1. Folding endurance

Both samples deteriorated and redacted the strength with time passes. Especially sample①, The numeric value dropped to less than 70% as compared with non irradiated sample.

1-3-2. Stiffness

Sample② ratchet downed the stiffness with time passes, but sample① had the inclination to temporary increased the stiffness by 100hrs and after ratchet downed it with time passes.

 

 

 

1-3-3. Tearing strength

Both samples ratchet downed the tearing strength with time passes.

 

 

 

 

 

Physical property
	Irradiation	Freeness	Basic	Thickness	Density	Ffolding	Stiffness	Tearing	Air tight
	time		weight			endurance		strength
	(hrs)	(cc)	(g/㎡)	( mm )	(g/cm^3)	(times)	( mgf )	( g )	(s/100ml)
Sample(1)	0	500	148	0.284	0.521	2411	1160	232	13.6
	50	500	149	0.284	0.525	663	1480	192	16.0
	100	500	149	0.287	0.519	593	1720	192	13.8
	150	500	147	0.290	0.507	509	1560	176	10.2
	200	500	147	0.283	0.519	273	1240	176	11.0
	250	500	146	0.281	0.520	263	1260	171	14.0
Sample(2)	0	500	155	0.292	0.530	1156	1260	230	17.8
	50	500	155	0.286	0.540	1461	1380	224	14.7
	100	500	157	0.292	0.540	1206	1280	208	16.1
	150	500	157	0.287	0.550	581	1120	196.8	17.6
	200	500	157	0.293	0.540	552	1100	188.8	15.4
	250	500	157	0.286	0.550	514	840	198.4	19.8

 

		Color difference
	Times		L	a	b	⊿E
Sample(1)	0		31.83	-1.18	-0.86	0.00
	50		34.46	-0.40	1.51	3.63
	100		35.87	-0.20	2.59	5.40
	150		40.71	-0.08	4.33	10.34
	200		42.91	0.18	5.18	12.69
	250		40.24	0.08	4.42	10.01
Sample(2)	0		26.13	0.12	-0.83	0.00
	50		27.03	0.06	-0.64	0.92
	100		27.27	0.06	-0.46	1.20
	150		27.19	0.17	-0.42	1.14
	200		27.77	0.24	-0.12	1.79
	250		27.90	0.12	-0.20	1.88

1-4 Fading test

1-4-1 Color difference

 We have applied relative color difference to valuation method. It’s defined by the followings.

⊿E = (⊿L²+⊿a²+⊿b²)^?

Relative color difference as “⊿E”

Color value as “L”

Color saturation as “a” and “b”

Each difference value as “⊿L”, “⊿a”, “⊿b”

In terms of variation for relative color difference,  sample② was prevented the degradation from progressing approx 1/5 as compare with sample①. Resultingly, It can be said to be useful for sun-proofed cone paper.

 

1-4-2 Visual comparisons

Passed 250hrs sample① had large progress of color fading as compare with at the point of 0hrs.

Passed 250hrs sample② had very small progress of color fading as compare with at the point of 0hrs.

1-5 Prospects

In terms of material development for sun-proofed cone paper, it can be said to be a complete successful development. However, in terms of physical property, it would have to say nothing to change as in the past. We’ll challenge next development that strikes a balance between holding the physical property and the color.

Development of a High Strength Pulp Material

1. Introduction
Ever since it was first commercialized in the United States in 1911, cone for loudspeaker, particularly those cones made of wood pulp have been posing new challenges and problems, many of which have yet to be solved scientifically.
Purasu Industrial Co., Ltd. has been engaged in the development of materials suitable for cones for loudspeaker and conducted research on beating and fibrillation of wood and non-wood pulp.
Although high freeness and internal loss are the necessary conditions, they are not the sufficient conditions for the loudspeaker materials. Different uses such as for TV, car audio, audio equipment require different types of material, making it impossible to work out a single solution that meets all requirements.

To develop UB pulp and commercialize it, it is necessary to:
(1) develop a beating equipment
(2) develop a beating technology, and
(3) evaluate physical and tone quality properties of experimental pulp.

To develop high strength pulp, we developed a beating equipment and beating technology, and conducted tone quality properties tests.
The definition of the ideal material given by paper-making industry is the pulp whose fibers are beaten and loosened but not cut, and swollen and softened so that internal fibrillation takes place to leave thin and long fibers undamaged.

2. Conventional Technology

　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　Diagram 1.Niagara Beater
As illustrated in Diagram 1., materials such as NUKP, USP, etc. at 3% to 4% concentration are fed into the Niagara Beater to proceed with the beating process. Since it uses steel blades, the Niagara Beater cuts pulp slightly as it beats. Since its own structure makes it impossible to beat pulp of over 4% concentration, the Niagara Beater can not beat pulp of high viscosity (high concentration) and keep long fibers uncut at the same time.
Since pulp concentration has to be low, fibers processed with the Niagara Beater are not swollen and softened enough. Another problem is excessive external fibrillation, which tends to cut fibers into smaller pieces. Although higher strength could be attained if blades made of lava are used instead of steel blades, the effect is limited.

3. Problems to be solved

The problems of conventional Niagara Beater are:

(1)Pulp concentration at the time of beating is 2% to 3% at the
most. When the concentration of pulp is raised to 10% or 15% for example, pulp does not circulate inside the beater. It is impossible to use the Niagara Beater to beat pulp of high viscosity.

(2) Since the blades of the beater are made of steel, they
unavoidably cut fibers during the beating process. At present, it is technically impossible to beat fibers and keep them undamaged at the same time.

New technology of beating is called for to solve these problems.

4. Measures to be taken to solve problems
　　　　　　　　　　　　　　　　　　　　　　　　　　　　　Diagram 2. UB Beater
The following measures have been taken to develop a beating machine which can process highly viscous materials in an optimum way.

(1)To avoid cutting fibers during the beating process as it happens
in the conventional method, we developed a method in which disks are used to beat and spread swollen material to proceed with beating process. (See Diagram 2.)

(2) To raise concentration of pulp material at the time of beating,
a screen ?idehydrator?j is built in so that concentration of material can be as high as 10% to 15% just before it is fed into the disk section.

The new method is called "Ultra Beating" (UB) from the way the material is processed.
5. Operation

5.1 Comparison of physical properties of different materials
Since the UB method can process pulp of 10 to 15% concentration, beating is done on semi-solid pulp and therefore, fibers are more swollen and softened and viscosity is higher. The material processed with UB method has the following properties.
The test specimen used in the measurement is a sheet whose weight per unit area is 150g/‡u, is molded in circle and pressed.

A.Air Permeability (air leakage)
Unlike conventional materials whose fibers are broken into smaller pieces, the UB-treated material is free of clogging problem and therefore, pressure-tightness is kept low.

B.Bending Strength
Bending strength is approximately 3 to 5 times higher than the materials processed with conventional method.
Among other materials, kenaf pulp has shown a marked change in properties before and after the UB beating. (See Table 1.) Kenaf belongs to Malvacede and is classified in the same generic group as hibiscus. The plant is grown mainly in China, India, Thailand and America. In China, kenaf grows mostly in Shantung and Hebei Provinces.
Kenaf grows to the height of 3m to 4m and thickness of 2cm to 5cm in approximately 4 to 6 months. When the plant has grown to this stage, it can be taken in and processed into pulp. Kenaf is a good substitute for needle-leaf and broadleaf trees as a paper material. As such, it is increasingly recognized as an ecologically-sound paper material of the future.
With regard to its properties, although strength is very low, stiffness is high even at low density. Its weaknesses can be overcome by the UB beating.

C.Tearing Strength
Since long fibers have been kept and twisting has been added, it has obtained the condition just like a twined rope (See photograph 1 and 2) and tearing strength nearly doubled. (See Table 1. Physical Property Test Data.)

D.Velocity of Sound Propagation
To measure the velocity of sound propagation, the speed has been calculated from the time it takes supersonic waves to travel on the Sonic Sheet Tester. The UB-processed material has transmitted supersonic waves approximately 5% faster than the conventional material. The difference in transmission speed comes from the structure of the UB-processed sheet in which long-stretched and twisted fibers are twined (See Photograph 2), increasing the tangency between fibers. As a result, efficiency of vibration (supersonic waves) transmission has become higher.

 

 

 

 

 

 

 

conventional method ....................................................................UB method

(Fibers are cut and crashed.)................................................... (Fibers are twisted and stretched.)

 

Test Specimen Weight per unit area: 150 g/m2

5.2 Relation between Freeness and Physical Properties

Unlike other materials treated with steam and chemicals, UKP material has its fibers mostly undamaged. That is why we have thought UKP material to be the optimum material to test the UB beating process which, theoretically, does not cut fibers. We conducted tests to compare the properties at different degrees of freeness.
The graphs 3 and 4 indicate the interrelations between physical properties and degrees of freeness. Bending strength rises as the degree of freeness rises, which means the higher the freeness, the stronger the resistance against bending.
Velocity of sound propagation rises most steeply between 600cc and 400cc of freeness, while stiffness falls in inverse proportion to velocity of sound propagation.
The fact that bending strength has shown the highest value at 300cc freeness proves that material is beaten in an optimum way in the UB method.

Graph 3 Interrelation between Freeness and Bending Strength

 

Graph 4 Interrelation between Freeness and Velocity of Sound Propagation

 

Graph 5 Interrelation between Freeness and Stiffness

 

Test Specimen Weight per unit area: 150 grams/m2

5.3 Fiber Length Distribution

To confirm whether the UB Beater beats materials without cutting fibers, we have recorded fiber length distribution (measurement of fiber lengths), using a fiber sorter. (Name of the fiber sorter: The Kajani Fs-200 Fiber Analyzer, Balmet Automation Co., Ltd.)

To prepare the material, we used both the Niagara Beater and UB Beater to beat Kraft Pulp (UKP) up to 500ml of freeness.
Result: The material processed with the UB Beater has fibers about 15% longer than the material processed with conventional method.

Graph 6 Fiber Length Distribution

5.4 Sound Property

The cone used in sound property test has been molded out of 100% UKP at freeness of 500ml. The shape of the test specimen is circle which is the basic shape and the diameter is 12cm which is the standard diameter for a full range speaker. The sound properties obtained from the measurement are shown on the Graph 5.

As indicated on the Sound Property Measurement Chart, the test material has produced a comparatively flatter line than conventional cone material between the range 1kHZ and 20kHZ.

Graph 5 Sound Property Measurement Chart

6 Conclusion

Higher elasticity and higher internal loss have been required of the materials for cones for loudspeaker in recent years and therefore, synthetic fibers such as carbon, rayon, Aramid fibers, etc. have been used mostly.

In this research and development effort, the objective is to return to the indigenous paper-making technique of Japan, using wood pulp-based raw materials to find the best material and the best way to process it. We have completed a method which does not cut fibers in the beating process and obtained stronger and more elastic material compared with conventional ones.

We are planning to use the UB beating method to treat different pulp materials to find their respective characteristics so that we will be able to find better combinations of different materials to have better physical properties, sound qualities and speaker uses in the future.